Search Results: he likes me but has a girlfriend

The obvious answer is “no” but hear me out:

I go visit my family for a few weeks after being away for quite a while.
I find out my younger brother of one year is practically juggling two women and playing the long game with both in hopes of getting one to be his girlfriend

Woman A is gorgeous, she’s also into him, they hooked up once already, he likes her too, it’s great. But she’s a little toxic

Woman B is a “rebel” with the tattoos and the metal bands and the easy going lifestyle with promiscuity and drugs and whatnot
She’s not into him at all.
He wants her, but isn’t settled on it.

Then I come on for a while and Woman B is all over me.
Under any other circumstance I would’ve spent half the vacation in a bed with her.

So I restrain myself as the good brother.
But I can’t help but wonder if I’m doing the right thing.

My brother has every reason to want woman A and she wants him too.
And yet he’s created this needless friend-zone wrinkle with woman B and it’s going nowhere (and I don’t think it should considering her lifestyle)

Part of me wants to fuck the socks off of woman B and I can’t deny it to myself.
I get the appeal but I wouldn’t date her long term. And she doesn’t want that either clearly.

So what would you do given this scenario?
Please give some reasoning and detail