My SO is very competitive, pitting his kids against mine. If they play soccer, he spends the whole time cheering his kids on and giving them tips on how to win. I try to stay neutral and I end up just being silent the whole time. I even try to convince them to team up on non-bio lines instead of always being yours versus mine but he never backs me up with that.
If my kids get something (they live with me) he goes out and buys the same things for his. If they have an argument between themselves (the kids) he always takes their side , like it's some battle. And he doesn't seem to get that this will only make my kids resent him and his kids more in the long run.
Are all men like this with their kids? His kids come to stay and then they complain if my kids are invited along by him to go grocery shopping (I have to remind him to ask mine along). At the dinner table, they only speak to him. They insist on sitting next to him. I try to make him sit them separately so that everyone is mixing but it's like I'm suggesting something out of order! When I suggest the competition thing has to stop, he just denies it.