If you sold the property to the family member, enter your interest income as "Interest from Seller-Financed Loans." In TurboTax this is a separate topic from "Interest on 1099-INT." The address that you enter is the payer's current mailing address.
If you are not the seller, do not enter the interest income as interest from a seller-financed loan. Enter it as if you got a 1099-INT, even though you didn't get one. Enter the name of the family member as the payer, and enter the amount of interest you received. It is not necessary to enter any other information about the payer.
In either case, you do not issue a Form 1098.
