The youngest son of Massachusetts Sen. Edward "Ted" Kennedy, he served as a Rhode Island congressman for eight terms.
But despite his success, he secretly struggled with addiction and a mental illness, which he wrote about in detail in a newly released memoir called "A Common Struggle."
Kennedy outlines a deep-seeded problem stemming from a painful history of substance abuse in his family, specifically his father and mother.
He believes his father self-medicated by drinking, never fully grieving the assassination of his two brothers.
Patrick says he is breaking the so-called "Kennedy code of silence," by releasing the book, but not everyone in the family is pleased with his memoir.
Kennedy's mother says she didn't know her son was writing a book, and she didn't help him with it in any way.
Joan Kennedy said she was not given a copy of the book and hasn't seen it, according to a statement she released through a friend, attorney Margo Nash.
A spokesman for Patrick Kennedy says Joan Kennedy was interviewed for the book.
In a statement, his older brother, Connecticut state Sen. Ted Kennedy Jr., on Sunday called the book inaccurate and unfair.
I am proud of my brother Patrick for his tremendous work to make mental health parity part of our national conversation and I admire him for his candor about his own challenges.
However, I am heartbroken that Patrick has chosen to write what is an inaccurate and unfair portrayal of our family. My brother's recollections of family events and particularly our parents are quite different from my own.
Our father was a man with an extraordinary capacity for empathy and intimacy who cherished many lifelong friendships; my dad and I shared a deep, emotional bond. Our mother has been fearless and forthright about her own addiction issues, but I strongly believe that her story is hers and hers alone to tell.
Mental illness and addiction are critically important issues that deserve a serious discussion -- not a narrative that is misleading and hurtful.
Patrick Kennedy defended his account Tuesday on MSNBC, saying, "All I can do is do the next right thing and pray that my brother will understand that what I'm trying to do here is bigger than both of us."
He also spoke to CBS' "60 Minutes," saying, "I don't tell, in this book about my family's stories as some way to talk about their story. This is my story. These experiences are embedded in me."
Patrick believes addiction is a family disease, and said he is "trying to bring light to all family stories" by telling his own.
With additional reporting from the Associated Press.