I regurarly have s** with my mother in law
I am very lucky in that I on average have s** 3 to 4 times a week usually twice with my wife and once or twice with my mother in law.
My wife is very open minded and we have a semi open marriage. My mother in law has been a widow for a very long time.
When my wife fell pregnant about 10 years ago with our first child, s** became an issue for her and was unable to have s** for duration of the pregnancy.
A lengthy discussion was held after my wife suggested I could have s** with her mother and all agreed this would be fine.
I feel very lucky as my wife and her mother are very beautiful and attractive and adventurous.
We do not have threesomes, we draw a line at that.