Martin Sheen felt "powerless" when his son Charlie Sheen had his public meltdown.
The 74-year-old star has confessed it was "painful" to see Charlie go through such hard times in the public eye but insists there was nothing more he could have done for his son.
Speaking about the 49-year-old actor's high-profile sacking from 'Two and a Half Men' in 2011, Martin said: "What he was going through at that time, we were powerless to do much. Except to pray for him and lift him up.
"You try to be as present as possible. But you have to be aware of the circumstances. You have to be aware of many things that the public is not aware of.
"Only those of us that knew him understood what was going on. I'm talking about steroids, at that time. He was in a very desperate situation. And he was doing what he felt would get him out of it - going public. And it was very painful. No less painful for him."
The 'Platoon' star embarked on a disastrous stand-up tour titled 'My Violent Torpedo of Truth/Defeat is Not An Option' after his now-infamous interview with ABC News' Andrea Canning, in which he claimed he wasn't bipolar but "bi-winning", following his axing from the CBS show.
And Martin - who is now almost 30 years sober himself after suffering a heart attack on the set of his 1977 movie 'Apocalypse Now' because of his heavy drinking - admits it was difficult to stand by and watch it happen.
He told Radio Times magazine: "You can assure them you're there and you love them, but you cannot effect chance. That's your ego, for the most part. You pray for a moment of clarity, you trust in a higher power and you never, ever give up hope. Because that is a measure of despair."