What caused this unusuall tire wear?

My brother's 2006 Buick Lacross started shuddering and he found this on his right front. Tires have 40k on them and are from Tire Discounters with 48,000 mile guarantee. Been rotated 6 times- do have a small leak- but never run it soft. Never curb damage or any other road hazard.

https://ibb.co/fgEoTb

This is likely a belt edge separation. How old are the tires?

Less than 4 years old--- this is the second set for the car.