In a new interview with The Hollywood Reporter, Kieran, 39, spoke about how his sibling's growing fame disturbed him - with 41-year-old Macauley reportedly commanding '$8 million paydays' for films in his youth.
Kieran recalled: "He would get harassed on the street.
"One time, a woman pulled off his hat and looked at him and said, 'Yeah, it's him! You're not that cute.' And then handed the hat back and walked away."
He continued to explain how he, Macaulay and their younger brother Rory were often mistaken for one another, saying: "When I was doing one of the Father of the Bride movies, this woman ran up to me and said, 'Are you Macluckly Macluckly?' And I went, 'No.'
"She goes, 'Can I get a picture?' I said, 'I'm not him.' And in my mind, I'm thinking, 'Nobody's that'."
Kieran also discussed his late sibling Dakota, who died at the age of 29 in 2008 after she was hit by a car, saying her tragic death is 'the worst thing that's ever happened to him - and is something that still impacts him to this day.
"There's no sugar-coating that one," he said.
"Each one of us handled it very differently. I think everyone was just torn up inside.
"What has it been, 13 years now? Holy s**t. That's crazy. Jesus f****g Christ. I accepted at the time that this is going to be forever, and it's never going to be fine. It's always going to be devastating."
He added: "I still weep about it out of nowhere. Something funny she did will pop in the head and make me laugh, and then I'm weeping. Sometimes it's knowing that she's not going to meet my kids and they don't get to have her, and it's hard to describe what she was like."
Earlier this year, Macaulay welcomed his first child with partner Brenda Song, naming their son Dakota, reportedly as a tribute to his sister.
In a statement to Esquire at the time, the couple said: "We're overjoyed."
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