updated 04/22/2011 AT 3:00 PM ET
•originally published 04/22/2011 AT 4:20 PM ET
Elton John and David Furnish surprised the world last Christmas with the birth of their son Zachary via a surrogate.
But there are still more revelations to come.
The couple have thrown open the doors to their home and their lives for a Barbara Walters special airing on ABC’s 20/20 Friday night.
Walters promises that some big questions will be answered about the new dads and their growing family, including: Which one is the biological father? Why in the world did they choose Lady Gaga as the baby’s godmother? And why did they take their shirts off in the delivery room?
During the interview, John, 64, reveals that the birth came earlier than expected and that the pair learned the surrogate was in labor while he and Furnish, 48, were out lunching and shopping.
He also says he was the one to cut the umbilical cord, after which he and Furnish both “took our shirts off” and put the baby next to their chests.
Explains Furnish: “They call it skin-to-skin bonding because it’s such a traumatic thing for a baby to come into the world.”