My boyfriend died but before he died he gave me everything. Now his family wants it back. Does it matter if their in my possession?

If your boyfriend gave you everything before he died it belongs to you, assuming that he was of sound mind when he did so (considering his subsequent suicide, this is a real issue) and that you did not exercise undue influence or defraud him into the gift.  However, with no will attesting to your boyfriend's intent or anything else in writing, and (I'm assuming) no witnesses, a court may not believe you when you testify that he gave you all his possessions before he died, in which case the property would pass to his family.  The fact that you have the stuff in your possession may, depending on the circumstances, help to convince the court that you are telling the truth, but it may not be enough by itself to convince the court.