Age gaps like this in fantasy and paranormal romance are incredibly common when you have fae, immortals, vampires, etc, falling in love with humans. Yes it gives a lot of people the ick but it's also something a lot of other people enjoy, you'll find your audience.

There are a few things you need to consider with age gap relationships:

power dynamics: if the two people in the relationship are on fairly equal footing in terms of social power, as long as one character isn't a minor, its generally fine. For instance, a 30 year old and a 40 year old who both work as sales reps in an office no one would really bat an eye at, but a 23 year old teacher dating an 18 year old who just graduated from their class rightfully grosses everyone out. Even though the second example has a much smaller gap, the power dynamic of teacher-student is too great to not feel predatory.

Maturity: The second big thing to consider is the maturity of the two people. Again I'll use the two office workers with a ten year age gap as an example. Both people are in a similar stage in life and would likely be dealing with a lot of the same problems, despite the ten year age gap, not a whole lot changes maturity wise in those ten years. As a counter example someone who is in their thirties trying to date someone who is in college. A person in their thirties would theoretically be fairly deep in their career and has no clue what it is currently like to be in college, which is what again makes it feel predatory.

What you're writing is commonly known as "man out of time" and a very good example of how it can be done and not feel weird is Captain America and Blackwidow in Captain America: Winter Soldier, or Aang and Katara in The last air bender. these relations have large gaps, but because the individuals are still locked in at that particular maturity level it doesn't feel weird or off

I love the ick in books when it’s a moral ick, not a re-used trope ick. Write on soldier

One, it's fiction.

Two, age gaps matter less when the younger person is 30+.

I think the age gap could work if the emotional connection is built carefully. For example, in The Time Traveler’s Wife, the age difference felt natural because their bond was so strong and real. As long as their relationship grows through shared experiences, I don’t think it’ll be an issue for readers

have you heard of twilight and ACOTAR? Don't sweat it.

Impossible age gaps are super common in fantasy where tons of immortal/very long-lived species or beings exist, and as a trope it has existed for as long as humans have created fiction (look at how many ancient myths exist of gods and mortals falling in love). If all parties involved are adults and you don’t feel uncomfortable writing it, go for it.

Age comes with wisdom, which is essentially knowing what's up. Because it's fiction people will suspend their disbelief so no need to REALLY worry about the ick as the audience will do the work for you and push the reality of the situation aside.

It all depends how you want your story to go and what you want to portray.

I'm writing fantasy also with an age gap, with one of the MMC's being hundreds of years old and I've made him a grey/leaning more towards villiane because although it's fantasy, I just feel that's who the bad guy would be by nature.

Being that old (500+) I just can't imagine a person seeing everyone else as equals. I don't view teens and kids as equals. They need guidance. They can be manipulated because they're growing but we often choose not to do that out of the goodness of our hearts but 500+ years?

At that point I just think people would become something we love immensely but not view equals... Like dogs.

Age gaps don't matter nominally but comparably, because it is not about the age itself as long as both are adults and completely developed, but how much and WHAT they lived as to have some common ground to connect, something in common. That is why you might have more in common in your 30s with an early 20s partner that worked since 16 and has a kid than a late 20s uni student living with their parents with no real life experience.

Age creates a gap (not the age gap itself) in relatability, but the older the two, the larger the tolerance for a nominal distance... EXCEPT for the fact that when we are talking about multi centuries old beings it is actually culture and how much the old one adapted throughout the ages that matters. Same thing as traveling through time

So the reason age is so important in our world is that everyone ages relatively the same and magical stuff doesn't happen like being frozen. Once you bring magic or alternate lifespan races in age literally is just a number and holds less weight. Basically it changes from caring about age to caring about life stage so baby, child, teen, adult, old, ancient. As long as the couple fits within the same life stage basically no one cares.

The only caveat to this that I can think of right now is if the older person saw the younger one grow up which you seem to have avoided.

As long as your protagonist isn’t a teenager, I think it’s fine.

By frozen in time, do you mean he didn’t age for several decades but lived as normal? That would mean he’s had several decades’ worth of life experience more than the FMC, so yeah, some folks might have an issue with it. As others have said, life experience makes a person wiser and more skilled in life in general, meaning they can influence their younger partner easily—so the power imbalance is there, whether intentional or not.

There are many ways to create a power imbalance, though. I, personally, do get tired of the MMC having age and knowledge over her AS WELL as having a community/friends/devout followers while she doesn’t, and having money and land, while she doesn’t—and usually he’s much higher status than she is. So there’s just a HUGE gap in power—but, sure, I can tell myself that a fae man who is 500 might have matured five human years every hundred years or something like that lol

If you’re worried about the imbalance in power, maybe make her have power over him in some ways—like a strong community that she leads, money, or land ownership. Or magic.

Are both the characters human? That can be another way around it, if the older one isn’t human.

I mean, we have a famous 70ish old guy dating a 20ish woman. Your example is far less weird.

If you look at the dark fantasy romance or romantacy subs, you'll see people requesting age gape relationship books (and other problematic themes). Write the story you want to write, there will be an audience for it!

One of the main issues with age gaps is that one has more life experience and that puts them in a better position to manipulate and exploit the younger person but since your character was frozen in time that isn't a issue. So anyone with any issue is probably nitpicking and has their own personal issues with age gaps

So while some just dislike any age gap I think one has to consider the nature of the age gap. One thing that makes age gap weird is the different level of experience. As a couple one is a team, if one is going through everything for the first time and the other has done this multiple times it get weird. The older one gets an authority as the more experienced one. So the question is what kinda experience did the man gain while in stasis?

Late twenties/early thirties is an adult, which is already leagues better than a teen. Also, while the male lead may have been awake during his frozen state, I can't imagine he'd have matured like a normal person would.

The main reason most people get the ick from big age gaps is the unbalanced power dynamic. The older person has so much more experience in basically everything, which often becomes a problem if they hold this over the younger person's head and force them into submission and over-reliance.

Sooo, a little ick to no ick for me, depending on the dynamic between them :)

I think your female protagonist is old enough that the age gap isn't as weird. Personally, the older you are when you meet someone with a significant age gap, the less ick it is. She's had time to experience life and figure out who she is. Then there are different things to take into account when thinking of an immortal character who perceives time differently versus a mortal character. The rate they mature may be slower. For example, a mortal character who is 30 may equate to an immortal (or longer life span character) who is in their hundreds. The best rule of thumb is that if you feel weird about it and don't like it, then change it.

Someone remind me but aren't Aragorn and Arwen in a similar situation? Then there's the attraction of Eowyen to Aragorn. No, I don't think this is an issue. Plus, it's about compatability and maturity, I'm sure you'll be able to make it work.

I don't see a problem with it, I think you should just go for it, let it unfold. I mix 300-plus-year-old women who look like they are in their 20s with 50-something-year-old men. Different maturity levels, heck, different worlds. In real life, people want what they want; logic isn't always in play. If someone is too prudish for what I write, then they should read something else. Go knock it out!

I wouldn’t even consider this an age gap, he was frozen in time so even though technically he was born like 60+ years prior, he’s still mentally and physically 30 so I don’t see any problem at all. Something like Twilight is icky because edward was mentally hundreds of years old, with your story it’s totally fine. If you’re worried about turning people off, just make sure it’s clear pretty soon that he was frozen in time both mentally and physically and you shouldn’t have issues with it

An immortal pursuing a teen to early 20s? That tends toward ick.

An immortal and a late-teens to early-20s who are thrown together because of circumstances/arraigned marriage/whatever, and are drawn to each other? Maybe not ick, especially if the immortal takes great care to encourage the personal growth of the younger person and tries to avoid influencing their choices too much.

The older the non-immortal, the less the ick.

Late 20s/early 30's is usually fine.

That not a bad one. In most romantasy I have seen age gaps of hundreds of years.

It's fine since the woman is fully an adult and has been for a few years. It would be weird and gross if she was under 18 and haven't lived as an adult yet.

Age gap relationships in fantasy almost always lead to power imbalances that create major ick. If you can find ways to avoid that, which would be refreshing and has been done once or twice in popular media, its not necessarily a deal breaker. Im working on subverting that myself in my novels.

Unike Twilight where the "17y old vampire boy", your Frozen in Time man in his late 20s, also had his emotional dev frozen, too. As far as I can see, a person who....jumped time, in a time warp, land +100y in the future....is still their original age +100y.

If the same person who 'went the long way around' (Doctor Who), they lived +100y of emotional (we all hope), spiritual, physical development so they are "current age" +100.

Hyper space and time Jump, Time Warp, Frozen in time.... they are their same physical and emotional age.

Actually, I have a YA story where the protagonist jumps xxxx years in to the future. They are still their same physical and emotional age. Timey Wimey thing.....time dilation, caught near a black hole

Age gaps are a social construct that only started to become a hot-button issue in niche circles online over the last 5 years. If it's not illegal, there's not really a damn thing that matters about it, especially if it's in your fantasy world.

It's fiction so age gaps are fine. Plus, it also depends on the setting. Some cultures do not have any issue with huge age gaps.