It's Matt keeping the closest thing to Mello with him, and Near letting it happen.

It's a bit like that when I write them. It's like: Matt is kind of a soft touch anyway, and he knows Mello gets something he needs from the both of them, so he kind of gravitates to Near after Mello leaves. And poor Near, he's always just a little clueless; I almost feel bad when my fic with him in it turns naughty. :-) I'll definitely post it when it's presentable.