The suspect wanted in the ruthless Brooklyn subway shooting that injured at least 29 people is a reclusive loner, relatives said Tuesday.

Frank James, 62, who was initially named a person of interest in Tuesday’s rush-hour N train attack in Sunset Park, has not spoken to one of his sisters in several years, she told the Daily Beast.

“I don’t know what might have been his motivation,” Catherine James Robinson told the outlet. “Last I spoke to him was like three years ago. We don’t keep in contact with each other.”

James, who police said has addresses in Philadelphia and Wisconsin, “kept to himself,” according to his sister.

“I don’t know what he was thinking,” Catherine Robinson continued. “I don’t know anything about why he might have done what he did.”

James is now considered a suspect in Tuesday’s attack based on “new information” that became available investigators, Mayor Eric Adams told WNYC radio.

The mayor did not elaborate and James was still at large as of midday Wednesday, roughly 27 hours after at least 10 people were shot in the rush-hour rampage aboard a Manhattan-bound N train as it pulled into the 36th Street station.

There’s no evidence that the gunman in Tuesday’s attack had an accomplice, Adams told MSNBC early Wednesday.

“It appears he was acting alone,” Adams said. “We’re asking New Yorkers to be vigilant.”

Of at least 29 people who were wounded in the mayhem, none have life-threatening injuries. Only four remained hospitalized, Adams told “Good Morning America” without elaborating.