bj,
My oldest sisters husband, 7 yrs older than me, used to tickle me also. He did this from the time I was 9 until I was 16, and one day lost my temper and someway flipped him over. After that, he would walk by me and try to trip me and hurt me on purpose. I told my guy friends about it at school, and they showed me moves to keep him from hurting me. I was the one who hurt him after that. My temper and telling myself he would not hurt me again got worse and worse. He finally gave up. It was for control, and I think after what I know of him a little later in his life, it was meant sexual also. It was his way of at least getting on top of me and dominating me, right in front of everyone. YUCK! I became a very defensive person for years because of this.