Son was with his friend, watching MILF porn. This got him to think about his own mom. Though much older than him, her mom is fuck-able. Age has not quite caught up with her, and son is thinking is all at possible for him to fuck her.
Opportunity struck, as he caught mom masturbating in the living area. he pounced on her and, though reluctant, mom finally gave in and allow her own son to fuck her silly.
In the other three scenes, it follows the same premise. Unsatisfied mom were pleased by their horny sons.
All moms got creampied!