My 7 yr old daughter and 5 yr old son got married this morning. (On kids terms, relax!)
About 10 minutes later, I overheard my 5 yr old son declare that he wanted to marry someone else.
Then came 8 yr old wisdom:
"You can't change now. You are already married. You can't marry 2 times. Once you're married, that's it."
Wish we all understood this simple fact.