I want to hang out alone with a friend of a friend.
Why do you want to hang out alone with them?
I'm planning on stealing all his friends so that he doesn't have any anymore.
It's great that you want to deep in your connection with a new friend, but you shouldn't do so through the exclusion of another friend. If you exclude your older friend from hanging out with your newer friend, then your older friend is likely to get jealous and resentful.
I don't care what he thinks, I just want to steal his friends and make him jealous.
I think it is great to make new friends but not good to betray a friendship. Everyone can be friends with each other, there is no reason that you need to steal them. Making someone jealous will hurt them and that is not something you would want to happen to you.