There is a way to designate relationships in FTM that states that they weren't married. If you go to the marriage notes tab, you can select the beginning status of the relationship. I usually pick "friends" or "partners" for folks who weren't married. You can also select the end status of "divorced" or "death of one spouse." If you put in a divorce date, it will automatically update the end relationship status to "divorced." I have yet to use the end status as I should for marriages that end in divorce that I don't have dates for, but I know it's a process that's going to take me time to update.