The Take That singer is currently expecting his fourth child with wife Dawn - joining kids Daniel, 11, Emily, nine, and three-year-old Daisy - but jokes he is more excited about how Robbie will deal with fatherhood when his wife Ayda Field gives birth.
Discussing the fact both he, Robbie and Take That bandmate Mark Owen are expecting, he said: ''Seriously, Dawn and I need to star getting things ready. But I think Mark's wife Emma is about four weeks ahead of us, so she is going to be first and Robbie is about a month behind us. But I think we are all most interested in Robbie's baby.
''I would love surveillance on Robbie's house 24/7 just watching him, especially deal with a baby. I am really interested to see how that is going to work. Let's face it, he is a big kid. But with everyone I know, having kids is the making of them, so I think the two of them are going to really love it.''
Gary believes Robbie and Ayda - who married in August 2010 - will be great first-time parents.
He added to the Daily Mirror newspaper: ''They are a very sweet couple those two. I always call them John and Yoko. They are very close and I think they are going to make a great mum and dad.''