Pennsylvania does a poor job of putting its statutes online, which makes it hard to look them up, so I'm going to answer generally and suggest you get a definitive answer from a Pennsylvania lawyer. In general, you have a limited time after an estate is closed to bring an action in relation to the distribution of the estate's assets, and seven years is a long time for revisiting an estate. If the amounts are worth pursuing and those who took the estate's assets have assets you can pursue, it's usually worth having the case reviewed by a lawyer to determine if it is possible to get relief, and to then handle the process of reopening the estate and attempting to recover the assets.

