You also need to know the other person's spending habits. Is someone the saver and the other the spender? Both savers? Both spenders?
This is stuff you need to know NOW, not later.
Is your mother-in-law a crazy person?
Probably, but can you handle it? Assume she's going to be around forever. She's going to drop in announced, invite herself to stay with you multiple times a month, and passive-aggressively insult your outfits.
You may really love your fiancé. But do you love him or her enough to deal with this woman for the rest of your life?
Is one of you going to change your last name?
If there is one thing I hear most often from my married girlfriends, it's that changing your last name is hell on Earth. Everyone gets confused: your employer, the IRS, the post office, and so on. People do NOT love when you change your legal name to something else.