Lionel Richie "freaked out" when he learned his youngest daughter was pregnant.
The 74-year-old singer has an adoptive daughter Nicole, 42, - who has Harlow, 16, and Sparrow, 14, with husband Joel Madden - as well as Miles, 29, and 25-year-old Sofia with ex-wife Diane Alexander and admitted it was surreal to find out the model is expecting her own baby with husband Elliot Grainge.
He told US TV show 'Extra': "I’m watching my baby having a baby. Yikes! I mean, that just kind of freaked me out a little bit. But at the same time, Elliot and Sofia are such a force. This little baby is gonna be souped up like you’ve never seen before. It’s amazing."
However, the little one won't have a traditional name for her grandparent, with Lionel revealing he will be known as "Pop-pop."
The 'Hello' hitmaker also revealed he keeps telling the couple to keep some privacy after they revealed the unborn tot's gender to the world with a pink confetti cannon.
He told 'Entertainment Tonight': "You know, there is no secret with those two! I keep saying, 'Keep it a secret, OK?' But yes, that's what's happening. I'm so happy."
Sharing his nickname for his grandchildren, he said: "I'm Pop-pop.
"We don't get the 'grandpa,' yeah, that's a little deep. Pop-pop is where we're going."
Model Sofia - who tied the knot with music executive Elliot last April - is six months pregnant but only announced the news on January 26, and explained that she had kept the news to herself for so long in an attempt to "protect" both herself and her spouse.
She told Vogue: "Pregnancy is really scary and you want to protect that space. I didn’t realise there are so many milestones you have to hit and so many tests you have to take. For me, it was really important to protect our mental health and our space as a couple.”