On your boy list, I don't mind
Leo though I don't like it enough to consider using it. I love
Jack as a nn for
John, but not as a stand-alone.
Brooks means 'pants' where I live.
Elias and
Ethan sound whiney to me. I dislike surnames as given names, which eliminates
Jackson and
Blake.
Kash is beyond dreadful.
I love
Caroline,
Penelope and
Norah;
Olivia is beautiful but too popular.
Adeline has pronunciation issues.
Amelia, with that whiney ME-E-E sound, puts me right off:
Emily is popular but would be much better.
Delia is OK;
Mia is trite but also very popular - two strikes against it.
So, for a combo I'd consider
Leo and
Norah or
Leo and
Penelope.
Leo and
Caroline seem to share too many sounds.