I recommend:
Absolutely NO rewards.....obviously it has not helped and it may have even hindered the process.
Tell Mom she MUST have him evaluated by a physician so that you can rule out if this is a medical condition.
Once you KNOW it is not a medical condition, you talk to Mom and, IN WRITING, come up with a Plan of Action:
Mom must put the older child in training pants (CLOTH UNDERWEAR) AT HOME. Ask the child every hour if he needs to potty (he'll say No) every 30 minutes, IT'S NOT A CHOICE, he sits on the potty. Repeat, repeat, repeat.
You -put a potty seat downstairs. Make it as private as possible.
Introduce both kids to the potty. Keep the kids in pull-ups, end then do the same as Mom. Ask every hour, not a choice every 30 minutes.
Again, no rewards....only lots of encouragement and your excitement and doing the "happy potty dance" after they have used the toilet!
Good luck!
