I'm about to marry a man who was convicted of a felony robbery can my daughters father who has joint custody take my custody away?

How recent was the offence? Is he on probation? Did he use a weapon? All of these are taken into account.

If the father can prove that your marrying this person puts your child in danger, then, yes its possible. But that could be very hard to prove. Just the fact that he is a convicted felon by itself is not enough.

The child's father can try, if he can win is up to the court and what evidence he can present. If this robbery was recent, was there weapons in his home? Was there violence in the robbery?

If he can win is unknown but he can try. Next it is not just marry, if he knows the man is just living there, he can try.