How to ask about 'EX-spouse' or biological parent.

[Angie Cranford]

Hey everyone.  I have a question.  My husband and I have had several rental properties for about 10-15 years now.  We have a property that is vacant and have several people look at it.  One potential tenant is a single mom of one child.  She is very nice, polite and has a good job and is going back to college to better herself for her and her child.  In doing the background check, we came across the child's biological father and looked him up.  He has several Civil and Criminal records that concerned us.  My question is:  Can we ask the potential tenant about the child's father?  If so, what is a polite but discreet way to do it?  I don't want to get into any trouble asking, if it is against the law. 

Thanks in advance.