Deductions & credits
Since this was his primary residence for 38 years, he qualifies for the capital gain exclusion on a primary residence and should report it as the sale of his main home.
Use the Sale of Home interview found under Federal > Income and Expenses > Less Common Income. Enter "main home" in the Search box and select "jump to main home" from the results.Only report his 25% share of the selling price and adjusted cost basis (this is unnecessary if no 1099-S was issued - see Sale of Home)
See the following screenshot for assistance in navigating:
