So, he's been living with her? Depending on the law in your jurisdiction he might be really fucked. If she's pregnant with his kid, he's definitely on the hook for that one. There's a provision in Canadian law I know where someone can be ordered to pay child support for a step-child if they have "stood in place" of a parent. So, if he was raising the jailbird's kid, he could be viewed as having taken responsibility for the child and be liable for child support. The legal principle is called "in loco parentis" and you might want to look into the rules in your area.