I truly don't understand. (And yes I know women do it too, I'm just having a moan).
I'm very lucky that this doesn't effect me in any way, but I feel so very sad for those kids (and their mums as well really). I'm talking in particular about my BIL. He has on the last count had 7 children to 5 different women.
And no he doesn't pay any maintenance for any of them. After his last marriage went tits up 2 years ago he disappeared, much to DH's dismay, (and my relief, I can't bloody stand the bastard). Him not being around has been great TBH, but I've also felt sad for DH as he missed his brother.
Anyway a month or so back BIL's eldest child messaged DH on FB to say he'd found his dad and been to see him. So DH started to message BIL on FB and they've been speaking. This weekend he's gone to visit him. Pleased for DH, but not so pleased he's back on the scene TBH but hey what can you do. Noticed DH has been tagged in some photos on FB earlier this evening by BIL (I'm not friends with him on there, but can see the pics DH is in). So I had a nosey at them and in the background of 1, is a little girl of around 14 months maybe. She is so obviously BIL's child (all his kids look exactly alike very distinctive eyes and hair).
I knew from what DH had mentioned that he had a girlfriend but didn't expect him to have another child so soon. 
He's probably spun his new girlfriend a load of lies and she probably doesn't even know he has so many other children, or that he isn't even divorced yet.
I mean that's 8 kids to 6 different women!
You're probably wondering why I give a shit at all seen as I don't like him? Well apart from feeling really badly for his exes and other children, it means that now DH is back in touch with him, at some point I'm going to probably have to see him, and his new girlfriend and new baby. Which means I'm going to have to keep my mouth shut and lie to this poor girl's face which I don't want to do. Or I don't see why I should bloody have too either. He made his own bed he should bloody lie in it. If I do say anything it would mean BIL would stop speaking to DH again, which would devastate DH. I'm caught between a bloody rock and a hard place really. Wonder if I can just refuse to meet up with him and his girlfriend would that work? I suppose it would unless they bloody turned up here, which I really hope they don't.