Wanting more sex

I married on leaving college having got my girlfriend pregnant then 19, it suited me as I would get my full inheritance instead of just my trust fund. I quickly added to my family getting my pregnant time and again. So, at 31 I'd 4 children and another on the way, my wife was having major trouble with that pregnancy. Her doctor recommended she get her tubes tied after the birth, I agreed she should as her health was very important to me. Sex was very important to me, and I only fucked my wife at the time. The baby girl was 8weeks premature and my wife very weak after the birth. So, her mother 47 (divorced) came to help out, mainly with the children. But as my wife was weak and needed a long recovery period, her mother started also providing me with sex. Just over a year after the birth of our last child my wife was ready to start providing me with sex again. But as her mother had been sharing our bed and providing me with sex with my wife in the same each time. There was no change to that, her mother joined in threesomes or one on one sex with me. Perfect arrangement for a sex mad husband like myself.