We are told that the product of the ages is 36, AlanF listed the possibilities.
We are told that the sum of the ages is a number which is not disclosed (number of windows).
At that point the friend says he needs another piece of information, so there must be more than one possible answer for the product and the sum specified. From AlanF's list, only two combinations give the same answer for their sum: 1, 6, 6 and 2, 2, 9.
I think the answer is 2, 2, 9, because the last clue is a reference to the oldest son, not oldest sons.