His mother catches them fucking and joins them to make a threesome

When their mother catches them fucking these brothers they think that their adventures of incestuous fucking have ended forever. And although at first mommy throws a good fight and stretches them from the ears so that they see how bad they have behaved, then the mature woman sees an opportunity to have a good dose of sex, because her husband has not fucked her for a long time. He tells them that if they fuck her she will also say nothing and let them follow their own as long as they want and fuck as many times as they want, so they end up doing a spectacular trio.