I think [name]Vincent[/name] and [name]Miles[/name] are both excellent choices for [name]Felix[/name]. They both have that underlying Latin etymology, tempered by much use in English and, in their own ways, on-trend.
Other names in similar trend:
[name]Otis[/name]. Other side of the [name]Milo[/name] & [name]Otis[/name] problem. However, [name]Otto[/name] and its Latin sound-similar [name]Otho[/name] are not similarly troubled.
[name]Titus[/name] and [name]Cyrus[/name] are similarly antique-but-wearable.
[name]Oliver[/name] and [name]Emile[/name] would be in the more-familiar, less-antique camp.
In any case, you have some wonderful options already! Good luck with the choosing!
Despite your reservations, these names from your list above are optimal together …
[name]Felix[/name] and [name]Leo[/name]
[name]Felix[/name] and [name]Linus[/name]
[name]Felix[/name] and [name]Milo[/name]
Additional ideas …
[name]Felix[/name] and [name]Arlo[/name]
[name]Felix[/name] and [name]Atticus[/name]
[name]Felix[/name] and [name]Augustin[/name]
[name]Felix[/name] and [name]Bruno[/name]
[name]Felix[/name] and [name]Cosmo[/name]
[name]Felix[/name] and [name]Ezra[/name]
[name]Felix[/name] and [name]Hugo[/name]
[name]Felix[/name] and [name]Isaac[/name]
[name]Felix[/name] and [name]Jasper[/name]
[name]Felix[/name] and [name]Oscar[/name]
[name]Felix[/name] and [name]Simon[/name]
[name]Felix[/name] and [name]Tobias[/name]
[name]Felix[/name] and [name]Viggo[/name]
I adore the name [name]Milo[/name] and have never heard of the cat connection that everyone is talking about. also, when I saw the question you had posted I immediately thought milo was perfect with [name]Felix[/name] before realising that it was one of your options already.
there are worst associations than cats anyway!
I say go for it!
[name]Felix[/name] and [name]Harris[/name]
[name]Felix[/name] and [name]Amos[/name]
[name]Felix[/name] and [name]Xavier[/name]
[name]Felix[/name] and [name]Wells[/name]
[name]Felix[/name] and [name]Vaughan[/name]
[name]Felix[/name] and [name]Vale[/name]
[name]Felix[/name] and [name]Tristan[/name]
[name]Felix[/name] and [name]Toby[/name]
[name]Felix[/name] and [name]Thane[/name]
[name]Felix[/name] and [name]Ridge[/name]
[name]Felix[/name] and [name]Ralph[/name]
[name]Felix[/name] and [name]Paul[/name]
[name]Felix[/name] and [name]Piers[/name]/[name]Pierce[/name]
[name]Felix[/name] and [name]Onslow[/name]
[name]Felix[/name] and [name]Nico[/name]
[name]Felix[/name] and [name]Leon[/name]
[name]Felix[/name] and [name]Tennyson[/name]
[name]Felix[/name] and [name]Cassian[/name]
[name]Felix[/name] and [name]Judah[/name]
[name]Felix[/name] and [name]Giles[/name]
[name]Felix[/name] and [name]Jared[/name]
[name]Felix[/name] and Hawke
[name]Felix[/name] and [name]Grey[/name]
[name]Felix[/name] and [name]Ezra[/name]
[name]Felix[/name] and [name]Eben[/name]
[name]Felix[/name] and [name]Edgar[/name]
[name]Felix[/name] and Nyall
[name]Felix[/name] and [name]Cullen[/name]
[name]Felix[/name] and [name]Claude[/name]
[name]Felix[/name] and [name]Cecil[/name]
[name]Felix[/name] and [name]Percy[/name]
[name]Felix[/name] and [name]Bentley[/name]
or
[name]Josiah[/name]
[name]Jonas[/name]
I personally love [name]Leo[/name] and [name]Felix[/name]. If want other suggestions though, I’d say [name]Simon[/name] or [name]Oscar[/name].
[name]Felix[/name] and [name]Leo[/name]
[name]Felix[/name] and [name]Simon[/name]
[name]Felix[/name] and [name]Oscar[/name]
I am also expecting twin boys! I love all your names. We have/had a few of yours on our list too. I [name]LOVE[/name] [name]Henry[/name] but would not use it because of the popularity issue. [name]Milo[/name] works well. Out of all your names though I think [name]Linus[/name] is the best choice. It balances with [name]Felix[/name] really well and they go together without being matchy at all. I also think [name]Oscar[/name] would be a great choice if you dont mind the odd couple reference.