Mets pitcher Bartolo Colon has been living a double life that gives new meaning to his nickname “Big Sexy” — siring two secret love children with a woman while married to his devoted wife of 21 years, The Post has learned.

The 42-year-old hurler has been dragged into Manhattan court by Alexandra Santos, 38, who claims the $7 million-a-year player is a deadbeat dad who failed to pay child support for their elementary-school-age kids.

Colon — who has earned more than $100 million in his career — sired the children with the Washington Heights woman while he was also playing the dutiful family man with wife Rosanna and their four sons.

The MLB star has never publicly acknowledged the 7-year-old daughter and 8-year-old son he had with Santos, who filed suit a year ago demanding child support.

“Mr. Colon obviously is a very talented baseball player and he earns a significant income, and we believe that his children should share in the lifestyle they would have enjoyed had their parents remained together,” Santos’ attorney Evan Schein told The Post.

Colon — who earned the ironic nickname “Big Sexy” because of his pudgy, 5-foot-11, 285-pound frame — was in Manhattan court Monday facing Santos in their child-support battle, which was listed in official papers as “Anonymous v. Anonymous.”

It was Colon’s own fault that his cover was blown. Because he briefly represented himself in the custody dispute, his name was listed as an attorney in the case, sabotaging the “anonymous” shield the former couple had been granted by a judge.

Court papers with details of the dispute are sealed, but records show Santos is asking a judge to force Colon to pay her legal bills and that both parties signed a confidentiality agreement in April.

Consequently, Colon’s attorney did not return multiple messages for comment and Schein declined to comment on the couple’s relationship or his client’s background.

Rosanna Colon, however, confirmed to The Post on Tuesday that she was aware of her husband’s second family and the pending lawsuit.

Reached at their Clifton, NJ, home, she said she’d known for some time about his other kids but wouldn’t elaborate.

“I can’t talk about that,” Rosanna said in Spanish. “This is personal and not something I want to talk about.”

The Colons are both from the Dominican Republic, where Bartolo met his future wife when he was just 13, according to a profile in the Cleveland Plain Dealer.

He and Rosanna became US citizens together in a 2014 naturalization ceremony the day before the Mets’ season finale. They have been generous toward their home country, providing scholarships, holiday meals, a baseball diamond, a chapel and even a training facility for aspiring sluggers.

Colon grew up poor in a hillside hamlet called El Copey, where he reportedly started strengthening his pitching arm by plucking coconuts out of palm trees.

Although guarded about his personal life, Colon has spoken proudly about his four sons with Rosanna — Bartolo Jr., Emilio, Wilder and Randy. But he has never publicly mentioned his fifth son or daughter.

Colon — who is slated to be the starting pitcher against the Washington Nationals at Citi Field on Wednesday — is due back in court with Santos next month.

The parties have only been in court two times since Santos filed suit a year ago. Their case was delayed when the prior judge overseeing it was promoted.

The revelation that Colon has a secret family is at odds with his on-field image as a lovable pitcher and the team’s heart and soul.

Fans were awestruck earlier this month when Colon hit the first home run of his career — setting a record for the oldest player to slam his first dinger in MLB history.

“Bartolo has done it! The impossible has happened!” Mets broadcaster Gary Cohen exclaimed at the time. The right-hander said the May 7 homer against the Padres was “probably the biggest moment in my career.” The hefty Colon trotted around the bases for a half-minute before reaching home plate.

Even Manager Terry Collins was stunned by the feat. “When it left the bat, I said, ‘Oh my God, he hit a home run,’ ” Collins said.

Colon — who signed his first pro contract at age 18 — is also the oldest active player in baseball at the ripe old age of 42.

He came up with the Cleveland Indians in 1997 and has played for eight teams, including a one-year stint with the Yankees in 2011.

Colon has a long list of professional accomplishments. He won the Cy Young Award in 2005, has played in three All-Star games and once threw 38 strikes in a row for the A’s in 2012.

He was crucial for the Mets in their run to the World Series last season, as a postseason reliever.

Before the news of his secret second family surfaced, Colon’s last black mark was testing positive for steroids in 2012. He was suspended for 50 games.

Additional reporting by Lorena Mongelli and Jennifer Bain