It made sense, really. Them. Together. The illegitimate sons, abandoned for convenience. And from what Max had learned of Ben's involvement with Vanessa (which was, of course, every sordid detail) he couldn't help but feel that this relationship was almost appropriate. 

He didn't really like Ben; just tolerated him. He was a buffoon, really - incompetent, useless in business and hopelessly well-intentioned. But Max didn't care about that. Ben was the most fabulously dominant lover Max had ever had; hot, demanding, and just his side of violent.

No, he didn't like his... brother at all, and somehow, that only made the sex better.