The boy asked his father

Boy aged: dad, I’ve decided to get married

Dad: wonderful, do you have a girl in mind?

Boy: yes, grandma! She said she loves me, I love her too.. and she’s the best cook and & storyteller in the whole world!

Dad: that’s nice, but we have a small problem there!

Boy: what problem?

Dad: she happens to be my mother. How can you marry my mother!?

Boy: why not?! You married mine!!