Gorayeb, 41 at the time of her death, was a single mom raising her child in Battery Park City. Her daughter was the result of a brief fling with a banker.
After the baby's birth, the dad, Edward Kranz, first denied paternity and later gave up custody rights in exchange for Gorayeb dropping her demand for child support.
So when the towers fell, the infant was in need of a mom, and Gorayeb's older sister immediately stepped up.
A marketing professional who was three months pregnant at the time, Claire Gorayeb uprooted her life in Boston, moved to New York City and, for all intents and purposes, became a mother to her niece.
With money from the 9/11 victims compensation fund, Claire rented and later bought an Upper West Side apartment for her niece, her biological daughter and herself. She paid for summer camp and a tony private school for both girls. She took her niece on trips to the American Museum of Natural History and to a summer home on Block Island.
To seal the maternal bond, Claire began the process of adopting Catherine's daughter in 2004.
Nine years — and many court fights — later, Claire is still trying to adopt her now 14-year-old niece.
The adoption has been challenged by Kranz, who had a newfound interest in the child's life after learning in 2004 that Catherine had died on 9/11. The adoption has also been delayed by a court-appointed guardian's scrutiny of how Claire and her family spent the 9/11 compensation awarded to Catherine's daughter.
On Wednesday, the adoption battle will come to a head when Claire and Kranz square off in Manhattan Surrogate's Court to determine what is in the best interest of the child, whose name DNAinfo New York is withholding.
Claire, 54, claims that Kranz disappeared from his daughter's life for four years and should have no say in the adoption.
"Since the tragic death of Catherine Gorayeb on Sept. 11, 2001, Claire A. Gorayeb has cared for her niece and provided her a safe, loving and caring home," her lawyer said in court papers.
Kranz, 50, of Murray Hill, claims that Claire shouldn't be allowed to adopt his daughter because she has blocked him from seeing her.
"[Her] best interests require regular visitation with me, her father," he has charged in court papers.
Catherine's daughter was born in February 1999, and a month later she filed a paternity suit against Kranz after he denied fathering the girl. By that September, a court-ordered DNA test showed a strong probability that he was the dad.
In January 2000, Catherine and Kranz reached an agreement where he withdrew any custody and visitation rights in exchange for her giving up on child support. He did not see or contact the girl for the next four years, according to court papers.
Raising a child alone suited Catherine just fine.
A tall brunette who always dressed sharply, she was known for her wit, adventurous spirit and irreverent pranks that left a lasting impression on ex-boyfriends, according to The New York Times.
Claire told the Boston Globe in a 2002 article that her sister embraced being a single parent. Catherine and her daughter lived in a Battery Park apartment near her parents and within walking distance of her job. She was always at the daycare center by 6 p.m. to pick up her child, Claire told the Globe.
On Sept. 11, 2001, Catherine was attending a breakfast business conference at Windows on the World when the planes hit the two towers. She died after making a final panicked phone call to her brother, according to accounts.
After the attacks, Claire immediately came to New York to be with her family. Eventually, she was laid off from her job at a Boston travel agency, but she relocated to New York City in order to raise her niece near her grandparents.
Shortly after the move, she was appointed the child's legal guardian and quickly formed a deep attachment. According to the Boston Globe article, the then 3-year-old niece vacillated between calling her aunt "Claire" and "mommy."
On Jan. 16, 2004, the child received a nearly $2 million award from the 9/11 victims compensation fund. Less than two weeks later, Kranz — who would later that year file for bankruptcy — popped back into their lives.
He called Claire to say he had just learned of Catherine's death while searching her name online. He would later claim in court papers that the years of silence were because he wanted to wait until his daughter had turned 5.
In February 2004, he mailed his daughter a picture of himself. Soon after, Claire filed for adoption in surrogate's court.
By June the fight had turned messy. Kranz went to family court to gain custody of the girl and have Claire's guardianship reversed, leading to the drawn-out legal battle.
In March 2012, a state appellate court affirmed an earlier Manhattan Surrogate Court decision that Kranz's consent wasn't necessary for the adoption to go forward and cited his long absence from his daughter's life.
But roadblocks to the adoption persisted.
Claire's refusal to allow Kranz visitations prompted a judge to appoint a guardian for her niece who questioned how the nearly $2 million 9/11 award had been administered.
Claire had transferred the funds into her own bank account and used the money to purchase a $900,000 Upper West Side condo that's in her name and her niece's, according to court papers. The guardian's audit prolonged the adoption process.
Kranz seized on the delay and petitioned the court for Wednesday's best interest trial.
In a response to Wednesday's hearing, Claire argued that she wants nothing more than to adopt her niece but that the delays are out of her control.
"At all times Claire has been ready, willing and able to adopt and has made every effort to move the adoption forward," her lawyer said in court papers.
Claire Gorayeb declined to comment on this story.
Her lawyer, Raymond Dowd, said he was not permitted by law to comment.
"This proceeding is confidential and private and is not open to the public, nor is its timing or occurrence a public matter," he said.
Kranz did not return a request for comment.
His lawyer, Robert Schnapp, declined to comment.