I was set a poser by one of my students a little while back and realised that I'd never quite got to the bottom of it.
She had found out that non-identical twins are known as fraternal twins, but she asked me if that applied to both boys and girls. I had to admit I had no idea. I'd never heard a feminine version, but working on the assumption that those houses in American universites are known as fraternities and sororities, I guessed there must be some equivalent.
So - sororal twins?! Sounds wrong to me, but then maybe that's because I've never heard it before. I've found listings for the words "sororal" and "sororital" but argument appears to reign over the use with the word "twins".
It's still just fraternal. It's the genes that are merely fraternal, not the individuals.