DP's youngest brother, 28 (who DP is very close to) has a really unhealthy idea of relationships. He gets intense very quickly and obsessed about women he starts seeing. Very old fashioned, Disney style romance type stuff and tons of slushy social posts after just a couple of weeks. He pays for absolutely everything for whoever he's dating, even though he's on an average salary and in debt. Some women have definitely clocked this and taken him for a ride money wise in recent years. What concerns me is that he tends to go for slightly troubled, timid women who he completely comandeers and treats like they're damsels in distress. Eg. Current girlfriend of two months has an eating disorder and is very shy and timid (a bit vulnerable I think). He is constantly talking down to her, telling her what to do, and wades into all normal day to day issues she runs into trying to be a hero. Past two relationships were exactly the same. It's weird.
DP is at a loss about what to do. His parents turn a blind eye and think this behaviour is fine if it makes their baby son happy. We see it as toxic. His relationships always end dramatically and with misogynistic accusations that his exes are 'psychos.' Any suggestions for how to maybe talk to him about improving his attitudes, or just let him get on with it?