I agree, I was just commenting on something I read to the efffect that Brian's obsession was rooted in trying to keep up with the Beatles, especially after hearing Sgt. Pepper's.
That, and the fact that his father was a nutjob.
Pet Sounds was released before Sgt Peppers. Some might suggest the Beatles (and the Stones with His/Her Satanic Majesties Request) was their effort to keep up with the Beach Boys.