If they aren't mon/son, they should be. They flow together. The playyfulness between the two. Brings back memories of mom and me. He needs to eat her pussy.
I still remember how it started between my mom (single parent and young) and me. When I was 10, I went over to her again and again at night and licked her vagina and from time to time also her asshole. A few weeks later we had the first real sex and I was allowed to ejaculate into her as well. Later also anal and oral. This went on for years and even led to pregnancies. Not to mention French kissing. Just awesome what we did
Mom has been fucking her son since puberty when she got his virginity. He has never had any other pussy because his mom lets him fuck her anytime he wants.