First of all, I appreciate you writing a gay couple in a prominent place in your story, and also making this thread to ask for input.
I would say, generally speaking, the biggest advice will be “you can write their relationship much as you would write a hetero one”; love is love no matter what, and every relationship will be different, just as all humans are, but you can write this as follows from who the characters are. But, sure, there are some things that are good to be aware of.
Context: I am another gay guy; also summoning my boyfriend, @ParrotWatcher, who tends to have a lot of useful thoughts about gay representation and suchforth 
He also has options about Greek myth, which may or may not come in handy 
I’d also note, there have been a lot of threads about similar topics in the past. (You could just do a forum search for the word “gay,” really ) I would particularly recommend looking at same sex relationships as probably the most directly relevant to your interests here. (It’s more about writing relationships that the main character is in, but there should still be pertinent stuff.) That thread did include a post in which I talked about a few ways that being gay can affect romance in ways that aren’t just based on society, but I don’t really see any of these coming up in your example.
So, these basic descriptions are fine, but one thing to be aware of is that depictions of gay relationships do often fall into portraying one as “the man of the relationship” and the other as “the woman,” which is pretty reductive even for hetero relationships (people don’t fit pigeonholes) and especially so when they’re literally both “the man.” So while you certainly can have one be more burly and one more fluid, just be aware that this won’t necessarily translate into every other aspect of their personalities and relationship dynamics. For example, maybe Hercules is the one who hangs around the kitchen in an apron.
(Like, I mean… I expect people would generally consider @ParrotWatcher a fair bit more masculine than me, but he’s also the shyer of us two, and sometimes I feel rather protective, etc. )
There can be a tendency for depictions of gay men to either make us all really stereotypically feminine, or go so far in avoiding it that any feminine characteristics are completely pushed aside, so it can be quite nice to depict a bit of both as you would be in this case. I’d just advise not exaggerating it too much; most people have a lot of traits that aren’t too strongly related to how masculine or feminine they are, just various other quirks or interests, so those are always good ways to characterize someone. I guess, just don’t try too hard 
(Describing them as going for polar opposites in masculinity feels like pushing them a bit much into being types.)
Now, for these guys in particular, also… I mean, it is Hercules you’re talking about, so I would expect him to be a pretty significantly musclebound he-man type anyway 
That’s something you can write just the same with him in a gay relationship as a straight one.
I’m not sure I understand what this means… could you explain? 
(I haven’t read Snicket.)