jokes about having sex w sister

Lanae🚼#✌️ • Mom of two 💙💗 Last of the bunch due May 2018 My ancestors had to shutup, I don't 😎
Is this okay? A guy I have been talking to. Not my boyfriend. Just talking to and have both made it clear a relationship is what we want. Anyway.
Today I got extremely irritated and offended. 
We were talking and he randomly asks for my older sisters number. They have never met. He may have seen a pic on fb. But anyway I asked why he wanted her number. He replies "to pay her husband back" (my sisters husband cheated) .. so I say "pay her back how?" He goes "I can have sex with her" 😒😒😒😒😒 should I stop talking to him over that? I really want to! He acted like it was a joke but I don't have time for these games. 
What would you do ?