Andy's grandmother Ellen Murray revealed the Wimbledon champ rang round relatives to tell them the good news yesterday, informing them Kim had given birth to a baby girl weighing 8lb 10oz.
Speaking to BBC Scotland, the proud grandmother revealed the sex was kept a secret during the pregnancy, so everyone was in for a nice surprise.
She said: "Andy and Kim said from the outset that they didn't want to know, so I'm assuming that they didn't know and of course none of us knew, so it was nice to get a little surprise like that."
Ellen continued: "Andy phoned yesterday and said 'Congratulations, you're a great-granny.' He told me the baby was 8lb 10oz when she was born. It's wonderful news. We watched him in the Australian Open final and I think he just wanted to come home.
"I don't really know about her name yet but I hope we'll see them all soon. I'll be looking forward to a cuddle."
So far neither Andy or Kim have commented on their new arrival.
The pair first announced the exciting pregnancy news back in August last year, and Kim missed out on a visit to Australia for the recent Australian Open as she was back in the UK preparing for the birth.
At the time, Andy vowed he'd miss the tournament to be at the birth of his first child if Kim went into labour while he was in Oz. "I'd be way more disappointed winning the Australian Open and not being at the birth of the child. For me, my child is more important to me, and my wife is more important to me than a tennis match."
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!