Marriage... Again

In the car as I'm driving myself and the kids to a baptism:

Shawn: Mommy, I will marry Kayla when we get bigger

Me: No, you'll marry another girl and Kayla will marry another boy, because you two are brother and sister."

S: No Mommy, I want to marry Kayla! (in a very big whiny voice!)

Me: Why?

S: (in that same whiny voice) Because I love her!

Me: Well, you love her because she's your sister, and you two will always be family. But you'll marry a different girl for your wife.

S: Noooo! I love Kayla!

Kayla: No Shawn, I must to marry another boy because you want to be a bad dinosaur when you get big. I must to marry a missiomary!

Needless to say he is still determined to marry Kayla