His criminal history has nothing to do with your visa application. He’s a U.K. citizen - they can’t ban him from his own country.
And the ILR application is about YOUR personal history, not his.
So, only YOUR criminal background is relevant, because YOU are the one who has to prove you deserve to live in the UK and won’t be a danger to society.
Which means that the only way your ILR can be refused based on criminal convictions is if YOU have any unspent criminal convictions on your record.