Yesterday my sister gave my daughters some hand me down dolls from her daughters. She just gave me a bag with 9 Barbie dolls. She watched the girls go through them and divy them up. She knew what was there. I was curious though, and today looked them up. Several of them appear to be fairly valuable. They are not in boxes, so not terribly pricey, but one seems to be pretty rare. My daughters want to save them for "years". DD1 already carefully sealed them in plastic bags saying she would save them until it was time for her to go to college, "by then they will be older and even more valuable". What is my obligation to my sister?