The girls insist on opening presents for their younger cousins and brother at birthday parties where the family is included. While this was acceptable when the younger cousins (and sibling) were too young to actually open their own gifts, it really isn't anymore. The mother has taken to appeasing them by allowing them to open one gift for their cousin that is the honored guest on a given day. This includes when she is not the hostess and has nothing to do with any of the party planning or anything. Don't ask me how they get invited to any one's parties because I really don't know. It seems this SIL's friends invite them all the time (perhaps she enforces better behavior at her friends houses).
These same cousins have also broken a brand new toy and chopped the hair off a brand new barbie doll that was a gift. When confronted, the mother's response? "Well, she'll never notice anyway, its not like it was a favorite toy or something."