LOL you don't owe them 49 each, you owed them 49.5 each because they let you keep the last dollar. So after you give them both 1 dollar, you owe them 48.5 to each parent.
They give you 50.00 each = 100
You KEEP 1, pay back 1 to each - 3 = 97
97/2 = 48.5
Everyone forgets that the parents let you keep the one dollar!