I’m officially expecting number three!!
If number three is a he, here are the ideas I have so far…
[name]August[/name]
[name]Spencer[/name]
[name]Harold[/name]
[name]Jasper[/name]
[name]Grover[/name]
Brothers are [name]Maximilian[/name] and [name]Felix[/name]. What do you think? Any more ideas?
None of these names especially strike me, though I think [name]Harold[/name] and [name]Jasper[/name] would make good brothers for [name]Maximilian[/name] and [name]Felix[/name]. Some other ideas could be: [name]Henry[/name], [name]George[/name], [name]Frederick[/name], [name]Roderick[/name], [name]Oliver[/name], [name]Samson[/name], [name]Xander[/name], [name]Knox[/name], [name]Dexter[/name], [name]Rex[/name], [name]Hendrix[/name], [name]Jaxson[/name], [name]Lennox[/name], [name]Jeremy[/name], [name]Phoenix[/name], [name]Gareth[/name], [name]Quinn[/name] [name]Billy[/name], [name]Robert[/name], [name]Desmond[/name], [name]Albert[/name], [name]Alexander[/name], [name]Isaac[/name]? 
I have a [name]Felix[/name] and know of three other Felixes who have brothers called [name]Jasper[/name] - it seems to be the go-to name for anyone who likes [name]Felix[/name] so we looked further afield. For our third boy we went with [name]Jarvis[/name] and we’re thrilled with it
I also had [name]Augustin[/name] on my list but DH wouldn’t agree. I think [name]August[/name] goes best with nickname [name]Gus[/name].
I really like [name]Jasper[/name] with [name]Maximilian[/name] and [name]Felix[/name]. I think [name]August[/name] would also be nice but I’m not a fan of any of the others.
Because of the X factor I like the already suggested name of [name]Knox[/name] and I have always liked [name]Jaxson[/name] spelled that way (I know a lot of Berries don’t) [name]Alexander[/name] is good also.
From your list I like [name]Jasper[/name] and [name]Spencer[/name]. [name]Grover[/name] and [name]Harold[/name] are my least favorites.
With [name]Maximilian[/name] and [name]Felix[/name], I think [name]August[/name] or [name]Jasper[/name] would be the best “fit” stylistically. Also, consider some names ending in “o” like [name]Hugo[/name], [name]Leo[/name], [name]Horatio[/name], [name]Inigo[/name] and [name]Milo[/name] as well as strong, classic names like [name]Victor[/name], [name]Laurence[/name], [name]Basil[/name], [name]Louis[/name], [name]Henry[/name], [name]Raphael[/name], [name]Oscar[/name], [name]Gideon[/name], [name]Tobias[/name], [name]Jude[/name], [name]Alexander[/name], [name]Oliver[/name], [name]Ambrose[/name], [name]Edmund[/name], [name]Barnaby[/name], [name]Casimir[/name], [name]Benedict[/name], [name]Vincent[/name] and [name]Josiah[/name].
[name]Jasper[/name] is my favorite from your list.
Others to go with the x theme: [name]Alexander[/name], [name]Dexter[/name], [name]Lennox[/name]
Others without the x theme: [name]Wesley[/name], [name]Lucas[/name], [name]Anton[/name], [name]Lorenzo[/name], [name]Blaise[/name]
I really love [name]Spencer[/name] and [name]August[/name]!
I really like [name]August[/name] and [name]Grover[/name]! To be honest, I really like all of them! Except [name]Spencer[/name]. It doesn’t fit with the others and is quite a bit too common for my liking.
Some others options are:
[name]Arthur[/name]
[name]Benedict[/name]
[name]Calvin[/name]
[name]Caspar[/name]
[name]Isaac[/name]
[name]Jonah[/name]/[name]Jonas[/name]
[name]Quinlan[/name]
Forgot to say i also like [name]Grover[/name] - I know four brothers called [name]Oscar[/name], [name]Jasper[/name], [name]Felix[/name] and [name]Grover[/name]!
Whatever you do, don’t lick another name with X in it - it’d be X overload.
[name]Love[/name] the names,
I love [name]Henry[/name], [name]August[/name], and [name]Theodore[/name] as siblings,
[name]August[/name] for me… Great name.