Legal Question in Family Law in Arizona

My condolences for your loss.

The biological parent has the right to take custody of the children if their custodial parent is deceased. If he is somehow unfit and it would be significantly detrimental for the girls to be in their father's care, then a non-parent who stands "in loco parentis" (in the shoes of a parent) may be able to petition the court for custody of the children; however, if the custodial parent is not unfit, then the girls may have to go with him whether they want to or not. I don't know anything about the family situation, but it might be worth asking the father whether he'd be willing to allow the girls to remain in the care of their stepfather (the father would have legal custody and the stepfather would have physical custody) so they are not further disrupted by their mother's death.