Your brother has a fairly good chance of section as his CAT percentage is well-above the required cutoff. For 2021, IIM Kozhikode cutoff was 85 (for general category students). But the selection depends a lot on the interview performance too. So, ask your brother to prepare thoroughly for the interview round.
You can go through the section criteria and the admission procedure of the institute to clear any doubts you may have.
Your brother has a good profile and a decent CAT score as well. So, it all depends on how the interview goes. He needs to give the panel a few reasons why he should be selected into the incoming batch.
One of my friends, who got 99.78 in CAT, was not able to convert IIM Kozhikode. Two years later, again he got 99.10, and that time around he was selected. For the first time, he was completely unprepared for the interview and it didn’t go well. For the second time, he was well prepared and confident.
The panelist looks for the candidates who are coming there to learn, not too worried about the campus job. It helps if the candidates are well-read and have a worldview, which will set them apart from most of the other candidates.
So, advise your brother to prepare well for the interview.