Levi Sanders is so far away from the political limelight that until his father began to gain momentum in his presidential bid, the press couldn’t even figure out the identity of his mother.

The only biological son of Jewish presidential candidate Bernie Sanders, Levi (pronounced LEH-vee, as in the biblical tribe name) has recently made his support for his father more visible, showing up on the campaign trail when it passed through his home state of New Hampshire and taking part in a kitchen table interview aimed at bolstering the often-grumpy Vermont senator’s image as a loving husband, father and grandfather.

Sharing a childhood anecdote with People magazine Levi said he had never called his father “dad” nor did he use his first name. As independent as his father, he chose his own version.

“When I was a little kid, I started with B. Then it was Ber and then Bern and now it’s Bernard. Or the Bernster,” Levi Sanders said in the interview. “I’ve never called him Bernie. And I never have called him Dad. Even when I was six years old, I thought it was childish. He was a friend, not an authoritarian.”

Levi Sanders, who is 46, works as a social security and benefits specialist at a Massachusetts law firm that represents clients whose benefit claims have been denied.

On the night of the 2016 New Hampshire Democratic primary, Levi made a rare appearance on stage next to his father and stepmother, Jane Sanders, celebrating the Sanders landslide victory over Hillary Clinton.

The elder Sanders has built his political career on a strict all-business style of self-presentation, shunning any attempt to dig into his personal life and preferring policy debate to social niceties. This attitude could explain the minor role his family has played in four decades of political activism.

As a child, family friend and fellow Vermont progressive Martha Abbot told VTDigger, Levi witnessed the meetings of the state’s Liberty Union party, the independent left-wing party to which the future senator belonged. According to the report, Sanders, a single parent with partial custody of his son, struggled to support Levi by working as a freelance writer by day while talking politics at night.

Sanders met Levi’s mother, Susan Campbell Mott, in New York City following his return from a short stint as a volunteer on an Israeli kibbutz and after his divorce from Deborah Shilling (who is now known as Deborah Messing). Mott and Sanders never married, but they did move to and live together in Vermont, where Levi, their only child, was born in 1969. The couple broke up several years later and had an informal shared custody arrangement.

It’s not known whether Mott, who now goes by her married name Susan Mott-Glaeser, is Jewish.

She still lives in Vermont and has declined to comment about her life with Sanders when asked by reporters.

Sanders never tried to hide his out-of-wedlock son, nor was it ever an issue in his political career as mayor of Burlington and later as a congressman and U.S. senator. But whether out of neglect or some other reason, Sanders never bothered to correct a 1981 news article, published shortly after he was elected mayor, that stated Levi was the son of his first wife. The mistake took root, and the record was corrected only after Sanders won national attention in his presidential race and reporters began digging into his background.

When Sanders married Jane O’Meara in 1988, the united family included her three children from a previous marriage, who grew up with Levi in Vermont.

Levi Sanders is married to Raine Riggs, a clinical psychologist. They have three young children, all adopted from China. His career choice, as an advocate for the rights of disabled people and others who were turned down by the system, seems to follow the path paved by his social-democratic father.

It may also be the case that Levi shares his father’s disdain for organized religion and public observance. He is not known to practice any faith in an organized way; a local New Hampshire rabbi, who asked not to be named, said he does not know whether Levi Sanders is involved in Judaism.

As a child, Levi once appeared briefly on a local TV show, standing in the snow and holding the microphone for his father while the progressive Burlington mayor spoke to residents. In 2006, he worked on Sanders’s first Senate campaign, drafting position papers on social security, welfare reform and health care. Levi then re-emerged on the political scene last August when he introduced his father at two rallies in New Hampshire.

Levi Sanders did not return calls from the Forward seeking his comments about his future role in his father’s campaign.

Levi’s three children helped their grandfather show voters his softer side as the candidate joined them trick-or-treating in New Hampshire last Halloween. For just a couple of hours, Sanders was a fun-loving grandpa knocking on doors with his adorable grandchildren — though he returned to campaigning that same evening.

Contact Nathan Guttman at guttman@forward.com or on Twitter, @nathanguttman