She wanted to feel her son inside her, she succeeded

She enters to fetch the dirty clothes and encounters such a spectacle. She had imagined it a few times, but for it to become a reality was just too much. Then the urge takes over her, and she realizes that she needs to give that young man a try. Just at the moment her daughter catches her, and with the maturity the occasion requires, she tells her that if she doesn’t have sex with her boyfriend, then mom has to do it. Therefore, we can deduce that they both had to share his cock and then took turns riding on him so he could compare both pussies. As usual.