In a Facebook post I referred to my daughter’s father-in-law as my relative.
Someone seeing the post and not knowing who Jim was might actually have through he was a biological relative of mine and wondered what the connection was.
Remember when interviewing family members that they may refer to individuals as “relatives” when they are not related in any biological way. They could have been related by marriage or could have been considered family for one reason or another.
Instead of trying force the “relative” to have a biological connection to your family, research them and see what the records indicate.