mayby my parents up front, but not my brother and sisters then they would start looking for an easy ride in life off me and not try in school. I would probably invest it all or buy some property. the place iam currently renting was on the market not long ago but didnt get sold, i would just make an offer to the owner, buy it then take it off the rental market. Just tell my housemate that she can just pay the bills and i will be happy or some sort of agreement like that[shes a good friend and very dependent financially so i would probably tell her]
the rest i would invest so my lifestyle wouldnt change all that much. Theres one or two other friends i would maybe tell, but everyone is sworn to secrecy, the others with the exception of a friend ive had since preschool are very well off so i doubt the money would make them think differently of me.
If you cant trust your closest friends i dont see the point, one of my friends brought this off once and he said he wouldnt tell anyone at all not even parents, just invest it all and live normally so when he is out of uni he will be set for life.
tl;dr my parents straight away, after a few months maybe 3 friends max sworn to secrecy including my housemate as i would buy the house so we dont have to piss away money on rent anymore.