Who do you marry

Ankit goes to India to attend Chacha's (Papa's brother's) marriage. He is a little puzzled with the whole deal.

Ankit: Chacha, why are you and Chachi getting married.
Chacha: We were in school together, and we liked each other. So we decided to get married.

Ankit is thoughtfully silent.

Chacha: What happened?
Ankit: I don't think Kevin and I can ever get married. Otherwise there will be two daddies.

Kevin is Ankit's friend in his school.