My opinion is that if he was touching you in any way that made you uncomfortable, it was wrong, even if "intent to gratify self" is denied. The situation you describe sounds like an incident of sexual abuse to me, especially since it did involve touching you on your rear end. Even if the last part of the memory were not included, this would be bad enough.

The fact that you were reluctant to approach him at first is a red flag. Children are sensitive to that kind of thing. Then the fact that he was not accepting of your reluctance is another one. It shows he does have boundary issues. An enlightened and sane adult would have let it go, and not coaxed you. It's a shame when a parent says to a child, "Now, stop that! Be a good boy and kiss Aunt Martha," if he doesn't want to. The lesson taught there is, your body is not your own, and you don't have the right to say no.

But it is, and you do. A child should never be made to be affectionate to any degree, if he/she doesn't want to.

Of course you didn't protest. You didn't know to. When the unrelated adult molested me at age 5, I didn't know what he was doing and had no way to attach "right" or "wrong" to it, but I knew it made me uncomfortable. When he didn't accept "no" for an answer, I went along with whatever he wanted me to do. Why? Because children are taught to obey adults.

A situation like this is NEVER the child's fault, even if the child does not resist at all. Not putting up a fight doesn't mean you were party to it. It means you were doing what the grownup told you to do, as any child would have done.