Considering how much they'd been drinking, I'm not surprised they had the idea to have a threesome. Especially since the mom is such a badass. Kissing your daughter in front of her boyfriend meant offering yourself up as a pussy for copulation. And the guy took advantage of that offer by banging both of them. He even shared his sperm with his mother when he came between his girlfriend's legs. Damn, that's fair!
Every man dreams of being woken up in the morning by such two charming girls. First they gave a blowjob with their mouths, then saddled up his shaft and had wonderful sex with him.