My brother married a widow with a son,the boy was never adopted .the mother of the boy died july2012 her husband died August 2012 with no will. What legal rights does the stepson have.

I believe the stepson would have inherited a portion of his mother's estate when she died. What he didn't inherit would have gone to the step-father. It is doubtful, after his step-father's death, that he would inherit anything more from the step-father. See this, which suggests he would inherit 2/3 of his mother's "moveable estate". The remaining issue would be what property (as distinguished from property of her husband) the wife/mother owned at her death.