PHILADELPHIA—Her name is Sarah Coyne. Not Sarah Trudeau.

To passersby she's just another sophomore at one of the world's most prestigious business schools. To those who know her on campus, she's not Canadian royalty but the sporty outgoing sorority girl who carries her weight in a backpack filled with economics text books.

By day she hustles around campus in a duffle coat, tuned into her iPhone as she lugs that backpack from class to class.

By night she helps organize parties and fundraising events for her sorority. In her spare time she tends to the books for the University of Pennsylvania's women's soccer club. And on occasion she finds time for the odd tennis match.

If not for her lineage, she would be just another student here.

But hers is the untold story of the only daughter of the Northern Magus — the provocative aristocrat with a dazzling charm who captivated this nation in 1968 and led it for 16 years as prime minister.

Sarah Elisabeth Coyne was just 9 when her father, Pierre Elliott Trudeau died.

Now 19, Trudeau's daughter has led a private life. Which appears to be the way she wants it.

Asked to speak to the Star on the 10th anniversary of her father's death, she replied simply: “I have no comment. Thank you for your interest.”

It was, perhaps, a response to be expected from the daughter of the man who took the state out of the public's bedroom. A private man with a publicly adored persona, he rarely spoke to the media after retiring from politics in 1984.

But unlike her father whose life has been the subject of books and film, very little has been written of Trudeau's youngest child.

Born May 5, 1991, in a St. John's hospital, Coyne's birth evaded the public spotlight that was shone on her three half-brothers who were born during Trudeau's years as prime minister.

In fact, the public didn't even know of her existence until four months after her birth when she became front page news after it emerged that Trudeau — then 71 — had been listed as the father on her birth certificate. Deborah Coyne, then 36, is her mother.

Little is known about the romance that led to her birth.

But Coyne and Trudeau were both passionate participants in the constitutional wars of the 1980s and '90s, fighting together to defeat the Charlottetown and Meech Lake accords, and Brian Mulroney's attempts to rewrite the Constitution. In the lead up to the Charlottetown failure, Trudeau and Coyne had a short-lived romance.

Neither party ever said much of the affair.

“I don't talk about my private life in public,” Deborah Coyne told the Star in 1991.

“I just won't comment.”

Trudeau's daughter is now a student of economics at the Wharton School (alma mater of Donald Trump and Warren Buffett) at the University of Pennsylvania — the Ivy League school in Philadelphia.

And she appears to have a politician's touch.

Working the ticket booth at the Cirque du Big Man on Campus — a sorority party/male dance-off meant to raise awareness and money for victims of violence against women — she greets many of the 1,100 in attendance with a welcoming smile as they enter the nightclub hosting the event.

Later, as she circulates, her popularity becomes clear. Boys greet her with a hug while her sorority sisters beckon her to the dance floor. She chooses to mingle with friends instead.

She is among the last to leave the party. Less than eight hours later she is back on campus, lugging her books from class to class.

A graduate of the University of Toronto Schools — the elite preparatory school on Bloor Street — athletics were a specialty.

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She was on the athletic honour roll for basketball, skiing, volleyball, soccer and track and field. She spent last summer working for a Kingston-based investment firm.

She appeared briefly by her mother's side when her mother sought the Liberal nomination for the Don Valley West riding in 2008.

But when her mother bowed out of that race, she reclaimed her privacy.

Shielded from the spotlight throughout her childhood, few details are known of Sarah Coyne's relationship with her father.

On the 30th anniversary of his rise to power, Maclean's magazine reported that Trudeau would visit Toronto once a month to see his daughter.

It's known that Trudeau did, on at least one occasion, travel with his young daughter. For it was on an outing in Niagara Falls in 1996 that a 5-year-old Sarah had a chance encounter with Jimmy Carter, the former president of the United States who was celebrating his 50th wedding anniversary at the falls.

Carter said the two ex-leaders spent several hours in pleasant conversation during that trip. It's unclear how 5-year-old Sarah occupied herself while the two men reminisced.

Sarah would meet Carter again four years later at her father's funeral in Montreal.

It was there that the public first glimpsed Trudeau's daughter as she emerged from a car outside the Notre-Dame basilica looking somewhat overwhelmed at the sight of thousands of mourners who lined the streets of Old Montreal.

Entering the church she nodded assurances to both Carter and Cuban leader Fidel Castro, who both reached down to embrace her.

“You're a very brave girl,” Carter said, patting her head and offering her a hug.

“I'm okay,” she replied.

Moments later she walked into the church grasping her mother's arm in one hand, a rose petal in the other, and took her seat in the front row.

Justin Trudeau did not mention her in his famous eulogy and Sophie Grégoire, his wife, has since said the two surviving Trudeau boys have had little interaction with their half-sister.

While her half-brother is touted as a future leader of the Liberal Party, Sarah Coyne seems content to remain out of the public eye.

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