Great question and very important:
-Can you see yourself growing old with this person?
-Are you happy to sleep with just this person for the rest of your life?
- will you love your spouse through the good times and the bad?
- in sickness and in health?
- do you trust your partner with your heart and with your life?
- are you willing to love them forever no matter what?
- do you agree on where to live, whether to have kids etc?
- do you have similar morals and goals for the future?
- who will do chores, shopping and housework?
- do you have similar ideas when it comes to financial maters?