I think men today have sorely lost touch of their responsibility (i'm not negating women, not in the least...there are some sleazies in the bunch!)....to their children, their wives, and their families....
the way to rectify a possible broken relationship is NOT to jump right back in. I'm 22...I know how vulnerable a 21 year old can be....i'm sure he's taking advantage of her to make himself feel large.....and he'll abandon her just the same. Trust- men don't do it once, get away with it, and change....
now my question is, how much does the 21 year old REALLY know about his family and the situation he's left the OP in? If she does, like another poster said, she DUMB with a capital D to think he won't do the same to her when it strikes his fancy and he wants to move on....its an ongoing cycle until someone breaks it and i'm sad to say the 21 year old won't be the end, i'm sure.
looking at my SO his dad had 4 babies by 3 different women and owed back child support to my SO's mom....he even told my SO once that (and I quote), "he could've just left him at the hospital and pretended that he wasn't his son"... right, because telling your child that makes it ALL better and reaffirms how much he's loved, RIGHT? jesus.