The columnist died of a heroin overdose in 2014, at the age of 25, and Bob has confessed that time hasn't eased his "unbearable" sense of loss.
The 69-year-old music star said: "Last week I went to the funeral of my mate's son. And he didn't want me to come for fear that I had to relive it. But I had to be there for him because it is unbearable.
"Time doesn't heal, time accommodates and it's ever present.
"You're driving along and you're at the traffic lights and for no reason whatsoever, the person in question inhabits you and I'll cry. And then I'll look around to make sure the people next door don't see me or are taking a photo and posting it or something.
"But that happens and that happens to everyone. And so you say, 'OK, it's time to cry now'. You just do it to the maximum because there's no use holding it in.
"Lights are green, or whatever, and then you go. That'll always be there and you accommodate that. Once you understand the nature of this because it is boundless and it is bottomless. The grief and the abyss is infinite."
The Boomtown Rats star had Peaches with his first wife, TV presenter Paula Yates. And he's now admitted to feeling lonely after Paula left him.
Bob - who married actress Jeanne Marine in 2015 - told 'The Tommy Tiernan Show': "You know that laser driven drive of a 16 year old clearly isn't there. And as you age it tempers, which you must understand at 50.
"By 68, it doesn't always need chemical assistance but it f***ing helps.
"And also you must be very careful because the beauty of a long married wife hides in plain sight and you must always look to that woman who animates you so that she once again electrifies you.
"And it's very easy with my Mrs who I've been with for 25 years. I'm sort of a one-woman geezer. And I'm not being soppy here but being happy together is such a turn on."
