The Take That popstar announced the news on his official blog earlier today (March 30).
"Hey friendlies, I've been keeping a secret from you all," he wrote.
"Me and Ayda are going to be mummy and daddy this year! We had sex! It works!"
He continued: "We've seen scans and cried. Looked at babies in commercials and teared up. The nursery is already planned.
"Basically I'm in love with a little person growing in mummy's belly. And can't wait to be a daddy... crying now. Much love much joy, Roberto, mum and little bump."
Williams is thought to be working on a new solo album, which was expected to be released in the autumn.
He is also currently planning another Soccer Aid UNICEF fundraising event.
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