As to the “stuff” this is a classic case of what I call the “pickup probate.” Which means: the first one to the house with a pickup wins. Cruel, but true. Yes, you can sue your grandparents and uncles, but pursuing such a case won’t be worth it unless the stuff includes some very valuable items.. You refer to probate of a will, so the will controls and an executor should be named. The house thus can be transferred to you by the will, but getting the stuff back is hard to impossible.
