The first issue is whether your father's records are good enough to be accepted in court as proof that your sister defaulted on the land contract. Just having his written records probably isn't good enough, do you have his bank records so the deposits from your sister can be tracked? The second issue is whether your brothers want to pursue a foreclosure action against your sister. There are three executors and you're only one of them, certainly your father's interest in this property is an asset of the estate and the estate can't be closed until either the executors give it to your sister or you take your sister's interest back and give it to yourselves.
Answered on Aug 15th, 2014 at 5:17 AM