Mortage Interest

My son & his wife is buying a house from his father-in-law.  The father-in-law is still living with them.  My son & wife has been making all the payments on the house/bills for a few years now.  They even went and refinanced the house and added my daughter-in-law's name to the house.  (She has better credit than my son.)  This happened in 2021.

 

When doing my son's taxes, how do I do the mortgage section?  I don't remember having to put the father-in-law's name is on his taxes before because his name is first on the 1098 and it's in his SS #.    

 

I got to the part when they asked if this is a refinance of a previous loan.  When they did the loan, it was a refinance of the previous loan.   

     Do I still put that this is a refi of a previous loan?

     Do I put that everything they refinanced went to the house, because it did?

 

Thanks.