The model died of a heroin overdose in April 2014, at the age of 25, and Bob admits it's still "impossible" for him to truly express the grief he's felt since.
The Boomtown Rats star shared: "When the deaths tumble on top of each other, my dad, my sister, that was tough anyway but when it's one of your children that dies ... the standard thing is that it's as though nature has gone into reverse but, more than that, you know this is a part of you in a literal sense.
"I mean you don't need me to emote on this, but if something that tough happens to you it's impossible ... it's impossible to define the fug of grief you descend into or to try and articulate that grief.
"In Peaches' case she ... she made a noise and she made herself felt.
"She was far too funny, too wild really and maybe, maybe a little bit too clever for her own good."
Bob believes he was raised "without authority" in his younger years, with his mother having passed away and his dad absent because of work.
The singer thinks the scenario caused him to become a very independent person - but he also acknowledges the downsides to his upbringing.
He told the Guardian newspaper: "When that happens you learn independence and organisation very quickly, but the downside is there's this dogmatism.
"There's no one to temper your rapidly forming beliefs and no one to show you the boundaries of what's permissible. You have to parent yourself and learn all these things. You have to invent your own universe."