I am so sorry for your loss.  You all have equal rights in the house if you were all left the house.  You all hav equal responsibilities as well.  I get the feeling that 4 of you are not so happy that one has moved in, especially since the house is on the market.  But the one moving in does not necessarily forfeit their inheritance by doing so.  If their moving causes monetary damages to the other 4 in some way - or to the estate I should say - then they can be held accountable.   Listen, maybe you should come up with an agreement between you as to the house.  If one wants to live there and maintain it until sold but agrees to vacate with in 30 days of sale or something like that - and please don't use this as legal dvice for a lease; seek legal counsel - that may be the best way to deal with it.  An occupied house may be better to ward against burglary, etc.  Good luck.