What would make a nice man from a normal, uncomplicated, middle class family choose to keep getting involved with women with so much baggage?

Oh I love the ducklings analogy!

I'd be careful if I was you. Life has a way of smacking you in the face when you least expect it. I say that as someone married for over thirty years with both DH and my DPs married for sixty years.
A couple of bereavements or an affair sending MH spiralling, and who knows where you'd be. I've seen it happen to those you'd least expect.

Some men like to feel they are rescuing a woman. It makes him feel like a hero

Im sorry but uf he has DC and DSC from his prior marriage even if he now only considers his DC his.. he has bagage too.

But you sound incredibly judgemental, and like your brother is "better" than these women.

I get it, would hate this for my son

‘We are outside of this a very nice normal middle class family’

So people who haven’t had the same opportunities as you can’t be nice or normal? I have 3 degrees and was left as a single parent, thank god my partner didn’t have the same views on me as you 😂.

It takes two to tango!

Your brother has chosen to be in relationships with these women because he obviously sees something in them. You might view their lifestyle as chaotic, but he may see it as exciting or spontaneous. Just because you've grown up in the same household doesn't mean you're going to make the same choices or be attracted to the same things. That's a bit short-sighted, to be honest. Siblings can be completely different people, with different personalities, values, and priorities.

What appeals to you doesn't necessarily appeal to him, and vice versa. That's just human nature.

The middle class upbringing is a red herring. Your brother has always needed extra help and care from your parents so the sign was always there.

Away from your parents guiding hand, he has led a life that is chaotic because that is who he is. He has baggage but you are seeing his baggage as somehow less than the women he has been involved with.

Your focus shouldn't be on the women he has been involved with and really you should see your brother as the person he really is. Also, bear in mind, you never know how he truly treats the women he is involved with behind closed doors.

I used to have a male friend who was intelligent, cultured and attractive who used to complain that he only attracted 'crazy' women who took advantaged of the fact that he had a good, well paid job and was 'empathic'. I learned later on that behind close doors he was abusing all his girlfriends and purposely targeted vulnerable, unstable women and of course no longer had anything to do with him. So the facade of middle class respectability and niceness just was a smoke screen for a predator.

This. If a man has one "crazy problem ex" I might,.just might, think there's a glimmer of truth in his story. It all his ex girlfriends are "crazy" then we have to look at the common denominator

Well, he is the common denominator in that story.

So I am not sure why you choose to criticise/blame these women and imply they are not good enough for him.

For all you know he thrives on drama or seeks these women because he has a saviour complex.

Or he might even have darker motives and targets women who are vulnerable in some way because he thinks they are easier to control and more likely to put up with a dubious partner because these women lack self-confidence. Or he might target vulnerable women with kids on purpose.

Frankly you need to get off your high horse and look at your brother with a more critical eye.

I used to have a male friend who was intelligent, cultured and attractive who used to complain that he only attracted 'crazy' women who took advantaged of the fact that he had a good, well paid job and was 'empathic'. I learned later on that behind close doors he was abusing all his girlfriends and purposely targeted vulnerable, unstable women and of course no longer had anything to do with him. So the facade of middle class respectability and niceness just was a smoke screen for a predator.

When mothers work full time, it tends to be because the father supports them and contributes equal parenting once they’re both home. Some fathers don’t do this, and so the mother isn’t able to work full time because they carry the full load at home. Is your brother one of those fathers?

Why would he expect his partners to work? The normal middle class lifestyle modelled to him as a child was a SAHM. I wouldn’t touch him with a barge pole because his family seems judgemental and toxic. How many people do you think enter into relationships expecting them to breakdown and them to end up with baggage? I certainly didn’t but here I am with baggage of my own… I’m just wise enough to know that single is better than a relationship with a man and a toxic extended family

She contributed X years of her life the same as your DB did.

Divorces are signed off by independent judges. If it isn’t fair, they won’t sign it off. It isn’t about being ‘weak’, there isn’t really an option thankfully to be either weak or strong; just a fair allocation to each party. Are you meaning by ‘contributing very little’ that he did far more in terms of both earned money, childcare and housework? Or do you mean she contributed little financially - because she was doing the parenting?

Life, or a child, isn't a vending machine where you put in a SAHM, married parents, own house and car, good education and receive a stable, well- adjusted, self -sufficient adult who will choose a respectable partner in return. Plenty of "well brought up" kids turn to drugs, seek out unsuitable partners, drop out etc. You're unreasonable thinking a comfortable upbringing innoculates someone from having flaws or issues.
You resent him, but all you're being expected to do is be nice to a few kids sometimes really. Just be happy that it's not your life that's complicated.

Weak or being a decent person?

When there's a pattern of repeatedly selecting low-income women, it's not a coincidence but his choice.

This is the root of your bitterness/enquiry isn’t it? That an unrelated person to your parents have got their hands on your parents money which you believe should be yours and your siblings. My advice to you is make your own money, support yourself; then you don’t need to get unhappy or ruminate about the whys of some money that you also haven’t earnt is going somewhere else.

Exactly. He's only interested in what he's getting from the situation. My NDN is married to a woman who already had 3 DC to someone else than they had one together....only after one thing.

OP, my brother has had two serious live in partners in his life (his ex wife and his current partner). In both cases, for different reasons, they didn't / don't work and he was / is the sole breadwinner. It seems surprising to me that after supporting his ex wife for around 15 years he would choose to be in another relationship with someone in the same position. His choice though!