Depends on the strains of the goldfish, it is possible for them spawning at 3-4" regardless of how old they are. Age goes out in the window in the fish world.
My Goldie's spawned at about 9 months old and 4" length.
I didn't want babies though so I didn't separate or feed them special so they slowly vanished. One of them lasted about two weeks I thought he'd make it. Nope.