How should the parents separate the children?

Sorry for the poor wording of the question i couldn't think of a way to put it.My aunt is getting divorced.They have 7 children(4 girls, 3 boys all adopted).There names are Lilly,Air (short for Aaron),Jason,Dylan,Tammy,Lexi,and Lulu (short for Lullaby).3 of the girls are triplets (Tammy,Lexi,and Lulu) and they have an older brother (Dylan) who also lives with them.The oldest girl (Lilly) doesn't get along with the middle boy (Air).Should the girls go with the mom and the boys go with the dad or some how separate Lilly and Air?Should the Triplets go with there brother?Should they have full custody or partial custody (few kids stay with the mom, few kids stay with the dad, parents switch kids on the weekend).Should the mom get full custody or the dad?Please answer and if you have any other thoughts on how to arrange the kids please put that in your answer too.