Feb. 22 will mark not only the day the legendary Massachusetts Democrat would have turned 81 had he not succumbed to brain cancer in 2009; it will also be the day his youngest child celebrates two years of sobriety.

He’s in town to help promote Lawford’s book, Recover to Live: Kick Any Habit, Manage Any Addiction — a guide filled with resources, information, self-assessments and interviews with experts on dependency and addiction.

Lawford, the son of actor Peter Lawford and Patricia Kennedy (the sister of former President John F. Kennedy), can relate to his relative’s struggle with substance abuse; he has been in recovery for 26 years.

His addiction started at the tender age of 12. “I was an angry, terrified kid who didn’t know it and I was looking to medicate that,” he says. “And drugs and alcohol were perfect.”

Wearing a dark suit on this windy January day, Lawford’s cousin and fellow member of the famed political dynasty is sipping a glass of water between bites of salmon. At 45, Kennedy seems a far cry from the lawmaker who made headlines and became the butt of jokes by late-night comedians following several brushes with the law.

Kennedy publicly disclosed that he had bipolar disorder to constituents in 2000 and said he initially was outed as a drug user by a roommate at rehab, who sold the story to the National Enquirer for $10,000.

The former congressman has also battled a prescription painkiller and cocaine addiction. In 2006, he crashed his car into a Capitol Hill barricade, claiming that prescription medications were to blame.

A Providence Journal editorial at the time declared, “He is likable, in large part, I think, for his refusal or inability to change much. He still seems a kid among the grown-ups. And he screws up as kids will.”

Time has transformed Kennedy’s boyish face, forming slight creases when he smiles. “I knew the last year of my dad’s life that things were going to change for good when he passed,” says Kennedy. The father-and-son lawmakers served at the same time for 16 out of the elder Kennedy’s more than four decades in Congress.

“I already knew it as I would visit with him and saw what life ultimately meant to him,” says the red-haired Kennedy.

“He wasn’t surrounding himself with politicians and celebrities. He was wanting to be with his buddies and his family members. And I said to myself, I would never want to be in that spot like he was in and not had what he had, which is three kids that were around him all the time, and his wife, and his best friends.”

He borrows the title of a previous book by Lawford, calling that time “a moment of clarity.” He says, “I thought to myself, ‘If I don’t make a change in my life, I’m not going to be able to have that.’ ”

Kennedy declined to run for a ninth term in office, leaving Congress in 2011. The longtime bachelor married Amy Petitgout later that year. The couple welcomed their first child together, Owen, last April, and recently settled in a house in southern New Jersey.

These days, life is different. “In Congress, I’ve been stuck. But I couldn’t stay stuck. That’s the nature of this disease. It’s a chronic illness and you’ve got to treat it on a daily basis. And you know outside of that constant hurried pace of life that you lead as an elected official, you have the chance to take it back a few notches.”

Rather than reminders for meetings or fundraisers, Kennedy gets notices about his son. He says with a big grin, “You know I have that in my Google calendar: Owen’s naptime. That really centers me. It pops up a couple times a day: Owen’s naptime.”

But he hasn’t stepped completely out of the public eye. He trumpets the nonprofit he co-founded, One Mind for Research, a nonpartisan group that works to do away with the stigma surrounding mental illness and brain injury.

He’s accompanying Lawford on a cross-country book tour. And he’s encouraging politicians to make mental illness part of the national conversation.

“I got my biggest reelection numbers of my whole congressional career after I got arrested and went to rehab. Now, I wouldn’t recommend anyone get a DWI as a means to get their highest numbers,” he exclaims. “But the point is, I went and talked about it after I got back from rehab. And instead of people turning against me, they turned with me, because they all acknowledged that in their own families they had issues.”

Lawford adds, “We’re going to get a lot more people well if there’s a culture of communication and trust.”

Kennedy has a sense of humor about his newfound role out of the political spotlight. He says with a laugh, “Now when I call the White House for any [Health and Human Services call] I just tell them, ‘Congressman Kennedy’s calling.’ They don’t know whether it’s Joe calling them, or Patrick,” he says, making mention of the latest member of the Kennedy clan to serve in Congress, the newly elected Rep. Joseph Kennedy (D-Mass.).

He doesn’t brush off the idea of running for office again, saying if he has another chance to serve it’ll likely be a few years down the road, once his son and 4-year-old stepdaughter are older.

“I love politics,” he says. “But the day before yesterday, my 9-month-old, unbeknownst to me while I’m taking a shower, propped himself up on the side of the tub and poked his head behind the shower curtain. And I thought to myself, ‘I’m the luckiest guy in the world to have that.’ ”

Photo: Former Rep. Patrick Kennedy in 2010.