There is a theory among the past life theorists that says not only do people have past lives, but that the people they met in those past lives will be met up again in this life.
Imagine for example two best friends growing up on a farm in mideviel europe, and today being partners in a food company.
The sex, race, religion, country of origin is totally random in these connections. You could be a french farmer in one life and an egyptian princess (or slave) in another.
So when you see someone that somehow reminds you that you met them before, but you can't put your finger on it, consider that maybe this person was with you in a past life.
You may have already been married to your husband/wife. In fact, maybe last time around you were the wife and she was the husband. Revenge at last . . .