Former Take That star Robbie shared his happy baby news with fans via Twitter on Monday night (28 April).
Robbie wrote: "Ayda and I are delighted to announce that Theodora Rose Williams is going to be a big sister. RW xx."
He provided no other details.
Robbie's tweet was shared nearly 8,000 times, with fans sending their congratulations in droves.
'Angels' singer Robbie and wife Ayda welcomed their first child together, daughter Theodora Rose, in September 2012.
They've nicknamed her Teddy.
Robbie shared a photograph of his daughter via Twitter shortly after her birth but since then, the couple have kept their child largely away from the limelight.
Robbie and US-born actress Ayda married at their home in Los Angeles, California in August 2010 after more than three years of dating.
Congrats to Robbie and Ayda!
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