Neil Patrick Harris: `David Burtka is the greatest dad`

The How I Met Your Mother star's son Gideon Scott and daughter Harper Grace reached the milestone on Wednesday, and taking to Twitter he decided to share the love with his fans.

He wrote, 'Things I dig: our twins Gideon and Harper, who are one year old today! They are glorious. So proud to be their Papa.

'And I'm in awe of, and so grateful for, David Burtka. He is, in my humble opinion, the greatest dad in the history of ever.'

The couple are finally set to tie the knot after gay marriage was legalised in New York State.

'David and I did propose to each other, but over five years ago,' Harris explained in June. 'We've been wearing engagement rings for ages, waiting for an available date.'