Should i invite my ex to move in (with his 4 kids)?

Long story short, I divorced from my son's father 7 years ago, after discovering he had a child outside of our marriage. I moved away to another state taking our son. This past year my son went to live with his father for the first time since the divorce. My ex has had a total of 4 children with the woman I left him with and has had Hell to pay for it ever since. I won't go into details, but she really turned his world upside down and he's looking like a rat on a sinking ship right about now. Its taken some time, but I've forgiven him for the betrayal. Our son is not happy living with his dad now, mainly because of the the actions of the mom of younger siblings there as well as another woman in the picture who is "not very nice to be around". Would it be admirable of me or just plain foolish to invite him to come stay with me until he gets on his feet? Let me make it clear that there are NO romantic feelings for him any longer, I just feel so bad for the guy. The irony is when we divorced I could have conjured up many terrible things I wanted to happen to him, but now that time has gone on and I've moved on I hear the things that he goes through with that woman and I think "man, I wouldn't wish that on my worst enemy". I think it would be a good change for him, our son, and those kids (who from the sound of things, are also going through a little hell with mommy dearest).