"Nothing in life is preparation for the loss of a child," the Bessette family said in the short statement, read at a news conference by family friend Grant Stinchfield.
"Each of these three young people, Lauren Bessette, Carolyn Bessette Kennedy and John F. Kennedy Jr., were the embodiment of love, accomplishment and passion for life.
"John and Carolyn were true soul mates, and we hope to honor them in death in the simple manner in which they chose to live their lives. We take solace in the thought that together they will comfort Lauren for eternity."
Lauren G. Bessette, a senior investment banker at Morgan Stanley Dean Witter, rose quickly through the ranks at the prominent Wall Street firm, where she worked for about six years.
Bessette, 35, was a passenger on the plane that crashed Friday night, along with pilot John F. Kennedy Jr and her younger sister, Kennedy's wife Carolyn
Bessette was promoted in December from vice president to principal. She specialized in Asian financial markets and worked in Hong Kong until about a year ago.
The department in which she worked is considered one of the most prestigious and challenging in the financial industry, according to a Morgan Stanley Dean Witter spokesperson.
"She's a wonderful person. She was very dedicated and professional," said Greg Neumann, a former co-worker.
Bessette was a member of the company's investment banking division in New York. While in Asia, she acted as a venture capitalist, setting up investment deals. Neumann had worked with her overseas and said she was admired by colleagues.
Bessette and her twin sister, Lisa Ann, were the first children born to Ann and William Bessette, an architectural engineer. Carolyn was 18 months younger than the twins.
The couple divorced when the twins and Carolyn were young, and their mother, a teacher and administrator at New York public schools, remarried a few years later.
Bessette and her sisters were raised in Greenwich by their mother and stepfather, Dr. Richard Freeman, an orthopedic surgeon, who brought the three daughters into the family.
A 1982 graduate of Greenwich High School, Bessette was a member of the all-girls service club known as the Signettes.
She graduated from Hobart and William Smith College in upstate New York in 1986.
Patrick McGuire, her college faculty adviser, described her as "a very bright, articulate, and very confident young woman."
Bessette majored in economics and went on to hold several financial market positions on Wall Street after graduation. She later earned her master's degree in business administration from the University of Pennsylvania's Wharton School, McGuire said.