I pronounce
Leila and
Lila differently.
Leila to me is "Lay-luh" while
Lila is "Lee-la".
I think
Stella and
Olivia would make excellent siblings.
Of your boy names, I definitely like
Henry and
Oscar the best, and I think they work perfectly as brothers.
If they're boy/girl, I'd go with
Stella and
Oscar or
Stella and
Henry.