Casey Affleck's "heart sank" when he realised he'd forgotten to mention his children during his Oscars acceptance speech.

Casey Affleck

Casey Affleck

The 41-year-old actor - who has kids Indiana, 12, and Atticus, nine, with estranged wife Summer Phoenix - picked up the Best Actor in a Leading Role prize at Sunday's (26.02.17) ceremony and though he paid tribute to his parents, brother Ben Affleck, co-producer Matt Damon, screenwriter and director Kenneth Lonergan, his friends, and fellow nominee Denzel Washington, his "mind went blank" and he accidentally forgot to thank his offspring.

Speaking backstage at Los Angeles' Dolby Theatre, he said: "

"Three seconds after I got backstage, my son said, 'You didn't even mention us.' And my heart just sank.

"My head was completely blank at the shock of winning."

And ahead of the Oscars, Casey - who stars opposite Michelle Williams as a troubled man who lost his children and is then forced to confront his past when he reluctantly takes on the care of his nephew in 'Manchester by the Sea' - credited his older brother Ben's success for helping him cope with life in the spotlight.

He told 'Entertainment Tonight' on the red carpet: "It maybe seems hard from the outside but he's had a pretty good time and I've had a weird life.

"I've been out here since I was 17 years old and so I've gotten to know lots of actors who have had a lot of success and some failures and some hard times and some success again.

"I've been able to see other people's careers and how they've worked out and it's been an education.

"And so I've really enjoyed my career. It's been exactly what I wanted and I feel very blessed and happy with it."