My wife helped me

After our third child was born, it was difficult birth my wife (32) went off sex. I couldn't blame her as she had a bad time with the last birth. She started concentrating on her career a lot more and sex was once a month at best. But with 3 children under the age of 6, she had her widowed mother (50) come and take care of the children and the house. We both have careers and I'm an engineer at the local power plant, working shifts. My wife knew I very liked sex and asked her mother to provide backup you could say. I hadn't been consulted or advised about their agreement. I got home after working all night had breakfast and went to shower, my mother-in-law (mil) joined me naked in the shower saying her daughter wanted her to provide backup for her. Shocked at first, but that didn't stop me from fucking my mil. The following week I was on day shift and at night my mil joined both me and her daughter in our bed. Sex is a lot more regular, and my wife has also started to join in threesomes with me and her mother. Not every time but enough to increase my belief she is getting over her reluctant of having sex.