You’d have a lovely lot of alliteration if baby brother also had an M name like [name_m]Morgan[/name_m] 
[name_f][/name_f] [name_m]Morgan[/name_m] has a lovely meaning too. I’d probably go for [name_m]Morgan[/name_m] [name_m]Michael[/name_m] [name_m]Clive[/name_m] M___ [name_f][/name_f]. If there’s a possibility you’d have a third child, would you feel restricted to choosing another M name? I don’t think you should feel that way, but just something to consider.
Some thoughts on each name ~
[name_f][/name_f][name_m]Morgan[/name_m]: in addition to above, it sounds distinct from [name_f]Maeve[/name_f], so I don’t think you’d mix them up too often.
[name_f][/name_f][name_m]River[/name_m]: one of my all time favourites. [name_f]Beautiful[/name_f] imagery and gentle vibes. [name_m]River[/name_m] [name_m]Clive[/name_m] [name_m]Michael[/name_m] M_ would be so handsome. Siblings would share the v in their name which is a nice connection but too subtle to be something you’d need to continue if you had a third.
[name_f][/name_f][name_m]Sonny[/name_m]: so bright and happy! Brings out the bright and playful side of [name_f]Maeve[/name_f] for me.
[name_f][/name_f][name_m]Isaac[/name_m]: A classic with a beautiful meaning. Goes well with [name_f]Maeve[/name_f] even though I find them quite different names, they complement one another. [name_m]Isaac[/name_m] [name_m]Michael[/name_m] and [name_m]Clive[/name_m] all have long i sounds. You might like, dislike or feel neutral about that, just something to consider with the name flow.
[name_f][/name_f][name_m]Jude[/name_m]: very cool, would make a really snazzy sibling set.
Suggestions:
[name_f][/name_f][name_m]Sullivan[/name_m], could have nn [name_m]Sonny[/name_m]
[name_f][/name_f][name_f]Sutton[/name_f], ditto
[name_f][/name_f][name_m]Remy[/name_m]
[name_f][/name_f][name_m]Asher[/name_m]
[name_f][/name_f][name_m]Jasper[/name_m]
[name_f][/name_f][name_m]Casper[/name_m] 
[name_f][/name_f][name_m]Beck[/name_m], another river meaning name and one syllable like [name_f]Maeve[/name_f]
[name_f]Love[/name_f] the above idea of [name_m]Ezra[/name_m] too