I understand the problem being faced by your brother.
There are two issues
1... Chronic diarrhea ( diabetic diarrhea ?)
2.. Urine incontinence.
There are several reasons why diabetic diarrhea is thought to occur. Sometimes it occurs because of overgrowth of bacteria in the intestines. It may also occur because of problems with the pancreas, which leads to poor absorption of nutrients. However, researchers believe that the most common reason involves a condition called diabetic neuropathy
Similarly dysfuntion of urination have long been known as a problem associated with diabetes and is due to autonomic neuropathy.
As this neuropathy progresses, it leads to incomplete bladder emptying, urinary dribbling, and overflow incontinence
You must consult a diabetologist
and a urologist
to have a joint management of uncontrolled diabetes
and urine incontinence.Simultaneously you can have consultation with a gastroenterologist also.