"The teacher rushed into my bedroom to tell me the good news, a bottle of champagne in his hands," Spencer, 49, tells the magazine. "Now, 31 years [since William's birth], my wife and I are with all nine of our children, and we're celebrating this family addition with just as much happiness."
Spencer's statement comes just as Kate's own mother Carole Middleton spoke out, telling reporters outside St. Mary's hospital in London today that her new grandson is, "absolutely beautiful." "They're both doing really well," Carol added. "We're so thrilled."
After Carole and Michael Middleton's visit, William's father Prince Charles and his wife Camilla Duchess of Cornwall made a stop by St. Mary's Lindo Wing, where Kate and her newborn are currently resting.
"Both my wife and I are overjoyed at the arrival of my first grandchild," Charles said yesterday in a statement about his grandson. "It is an incredibly special moment for William and Catherine and we are so thrilled for them on the birth of their baby boy. Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future."
Rounding out the family and friends paying a visit to Kate, Will and their 1-day old baby was the Duchess' hairstylist, who visited the hospital today in preparation for Kate's first post-baby debut.
Earlier today, the Tower of London held a 62-gun salute honoring the birth of Will and Kate's son. Simultaneously, the King's Troop Royal Horse Artillery fired a 41-gun salute in Green Park after riding past Buckingham Palace.
Kate gave birth to her and William's royal baby on July 22, 2013, at 4:24 p.m. local time. The newborn weighed in at eight pounds and six ounces. The royal couple has yet to announce the name of their new bundle of joy.