If you don't handle a marriage proposal by accepting or rejecting it when it arrives, the game will automatically accept it for you if you quit the game or it crashes. That's why the person was in the house when you opened the game again.

Unfortunately, crashes can do unpredictable things to any application, since it doesn't get to close gracefully. It's hard to say what long-term effect this will have on things.

What version of Virtual Families are you running? If you don't have the 1.1.1 update yet, you should update the game, since it has some important improvements that help prevent crashing on most devices. Also, if your family is at the 30th generation, there is a bug in version 1.0.0 that will cause serious problems with the game.