I think having some sexual experience with your mother in law is very erotic. The first time my mother in law saw me naked was very erotic for me. I had finished doing some work at her house. I was in the bathroom washing up and was nude. The door was open. She came home from work and came to the bathroom. I turned to face her and got an erection. Her eyes looked at my cock and she smiled. She asked what I did that day. So we walked around, I still naked and erect. She had brushed against me a few times.
When I finished showing her what was done and what was remaining I asked if she had some aloe or vitamin E cream as I had a rash. She awaked where it was as she got the cream. I showed by my testicles. She then put some on her hand and rubbed my testicles and leg. We did this for almost 2 weeks as I worked slowly.