I remember a fic where dean and Sam were both half angel. their mom was an angel, and dean woke up one morning with wings John  freaks out and tries to cut them off. Dean goes to Sam to warn him. when Sam's wings come in, some angels come to kill them. Michael and Uriel I think. they think Sam is evil and try to kill him until, Dean makes his own sword after Sam already had.
does that ring any bells? I think it might be in FF.net