Web site, Jay McGwire looks to be a dead-ringer for his older brother (and not quite as tan as the photo from Deadspin to the left). A professional bodybuilder, Jay supposedly claims in the book that he introduced his brother to steroids after Mark saw the effect the drugs had on his younger sibling.
According to Deadspin, one excerpt from the book reads:
Shortly after I won the Contra Costa Bodybuilding Championships in May of 1994, Mark took the plunge. I accompanied him to Sacramento where we met with my supplier and trainer, who explained to him how the different drugs would work on his body and answered a myriad of questions from Mark.Once his brother got big from steroids, Jay allegedly claims that he introduced Mark to "andro" -- the steroid-like drug found in the then-Cardinals player's locker in 1998 (the year he hit 70 homeruns) and banned by major league baseball in 2004.
Surprisingly, Deadspin reports that several publishers have passed on the book. Less surprising is news that Mark and Jay had a falling out years ago and haven't spoken in quite a while.