I think it's better to treat twin girls as a normal sibset and not as twins.
Any way out of your names I like
Nina and
RubyNina and Kaya
Nina and
IrisNina and
JuliaNina and
Sophia
I think it's kind of problematic that almost all your names end with -A and that most of them are four letters long. Some how they all seem a bit too themey (except for
Iris and
Ruby)