My other thought is that some medications have short term memory problems as a side effect. Is your brother on any medications ? If her is, he could go to www.drugs.com , type in the name of the drug and see if memory issues are a side effect. Finally, is your brother having sleeping problems ?
For some vehicles, you're advised to change the coolant every 30,000 miles. For others, changing the coolant isn't even on the maintenance schedule. For example, Hyundai says the coolant (what many refer to as antifreeze) in most of its models should be replaced after the first 60,000 miles, then every 30,000 miles after that. The interval is every 30,000 miles on some Mercedes-Benz models, but on others it's 120,000 miles or 12 years.
If it goes below 32 for long you could have a problem. It takes me about 15 minutes to pump (using the water system pump) antifreeze in all the lines and what goes down the drain protects the traps. About the same amount of time to de-winterize. 2 gallons of antifreeze and 30 minutes work could save a lot of headaches.