Irish boxer Michaela Walsh has said seeing her brother Aidan secure an Olympic medal has brought her "a joy I've never felt before".

The Monkstown Boxing Club fighter is guaranteed at least a bronze medal following his welterweight quarter-final win over Merven Clair of Mauritius.

He will have an opportunity to upgrade that to at least silver when he faces Britain's Pat McCormack in a semi-final at 4.03am Sunday (Irish time).

His sister, whose own Olympic journey came to an end earlier this week after she lost to Italy's Irma Testa on a unanimous decision in their last-16 women's 57kg featherweight bout, said it was "unbelievable" to see her "baby brother" achieve one of his goals.

"I'm immensely proud of him and the performance he had," she said when speaking to RTÉ Sport from Tokyo.

"Everyone at home is buzzing for him."

She said that during the pre-Olympic training camp, Aidan was focused on his performance in the belief that the medal was going to come.

"Even in the training camp he was just focusing on the sparring, trying to perform the best in the sparring and he took that approach into Tokyo and has been focusing on the performance, each fight at a time," she said.

"He's not been looking too far ahead and he’ll come back and regroup and then look forward to the next one.

"For Aidan, the main focus is performing to the best he can be and the result takes care of itself."

Walsh said her brother was "ecstatic" when she congratulated him after his quarter-final success, saying she wasn't sure if the gravity of achievement has hit home yet.

"I just said to him 'Aidan, you're an Olympic medallist’ and he was just ecstatic. I don’t think it has sunk in for him," she said.

"To be an Olympic medallist is something so special, something we've both dreamt about, so to see Aidan do that is just unbelievable.

"I would almost give my dream up for him to achieve his, that’s how much it means to me, he’s my baby brother.

"I’ve been there the whole way through the journey and the pride I have is unbelievable, I can’t describe my emotions at the minute."

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