She never said anything to me. I don't know that I could own up to anything without making it worse for my niece. I suspect she may have told others that I made her feel uncomfortable, and that is why this all happened, or it's also possible that K was the one who made an issue of it in the first place ( I have good reasons to believe that this may be the case).

I just try to stay away from my niece when we're at family functions. I hold nothing against her, I feel terrible that I made her feel uncomfortable in any way.

Perhaps you're right. I could try to be the better person, but it doesn't change the fact that I never liked K much in the first place, and see no reason to spend any time with him at all.