Gary Barlow has revealed the boy band - made up of Howard Donald and Mark Owen, and former member Jason Orange - express continuing concerns for their pal, who recently opened up about his mental health struggles, because he tends to occasionally ''lose it a bit''.
Speaking on ITV's 'Lorraine', he said: ''It is a bit of a thing with Rob that he's just designed to just, now and again, just lose it a bit. He loses his way a bit.
''It really goes to show how sort of haunted he is by that side of his life.
''We all worry about him constantly. He's still to us the baby of the band.
''He was 15 when he joined Take That, he wasn't even 16.''
Robbie spoke out about his mental health struggles earlier this year, admitting he has a ''disease in his head'' that wants to ''kill'' him.
He said: ''Fortunately and unfortunately, left to my own devices, I'm inclined to sabotage everything. I've got a disease that wants to kill me and it's in my head, so I have to guard against that.
''Sometimes it overwhelms me and sometimes it's a tool I need to get on stage.
''Sometimes I live in bliss and it's wonderful. But most of the time I'm human - having a human experience, trying to deal with the trials and tribulations of what goes on between my ears.''
Robbie - who has daughter Teddy, five, and son Charlton, three, with his wife Ayda Field - has made no secret of his mental health battle in the past and has opened up numerous times about his drug and alcohol addictions.
The 'Candy' hitmaker also suffered a health scare last year when ''abnormalities'' were found out his brain - meaning he had to spend a week in intensive care.
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Sometimes actors are not acting.