Welcome to HCM
Your brother is having diabetic coma
which is a serious complication of high blood sugar level that is diabetic keto acidosis
, if there is no other complication with treatment he should improve gradually as he is already treated in hospital.
In such cases correction of dehydration
and if there is infection antibiotic is logical treatment , he should respond well to treatment.
He is receiving best possible treatment and we should hope for best.
I wish him a speedy recovery.
Best of luck