I think I have a possible answer...
All same birthdays. Pregnancy lasts 9 months. His wife was unlikely to be able/willing to have sex with pregnancy as an outcome three months after giving birth.
This writes 18, 2, 1 and 6, 3, 2 out. This leaves 9, 4, 1
The problem with this is that it means the door number and the piano thing are irrelevant and that is unlikely..