Billy T James' wife, Lynn Matthews, resides in New Zealand. She became a widow after James died in 1991 at Greenlane Hospital in Auckland on August 7 after a heart failure. 

James had a serious heart attack in 1988 and underwent a quadruple bypass. However, he required a heart transplant in November 1989 because of the previous unsuccessful procedure.

In April 1990, during the variety show Billy T James, Alive and Gigging, he returned to the Aotea Centre stage. But shortly after that, he had another heart failure which claimed his life. 

The pair is said to have married in the 1970s, but the exact date is unknown. He married Lynn, who was his daughter's aunt. Cherie was the daughter of Lynn's sister and Billy.

Lynn collaborated with Matt Elliot, who published a biography about him almost two decades after his death. James' first biography was published in 2009. The author, Matt Elliott, used interviews with more than fifty of Billy T. James' acquaintances and coworkers, as well as with his wife Lynn and sister Ngaire, to create The Life and Times of Billy T. James.

It was also turned into a movie that received funding in December 2010. In the movie Billy, Morgana O'Reilly is Billy's wife Lynn, and Tainui Tukiwaho is Billy. The movie had its TV One premiere on August 21, 2011.

During that time, his wife appeared on media and shared with people about her husband's life. However, since that time, she has remained away from the limelight. 

Billy T James's daughter Cherie worked with him on The Billy T James Show in the late 1980s. She is the daughter of Billy T James, but with Lynn, she has a relationship with both aunt and a stepmother. 

Following her father's death, Cherie launched her screen career. She featured in a documentary titled Billy T James - A Daughter's Story in 1997, where she talked about her famous entertainer father. After studying performing arts at Unitec in Auckland, she obtained a brief role on the television series Mercy Peak.

She was nominated for Best Actress at the 2003 New Zealand TV Awards thanks to a cameo appearance on the Mori supernatural series Mataku.

After portraying a resentful family matriarch in the television series The Market, she was nominated for an Air NZ Screen Award in 2006. In the short film Point Annihilation, she played a mysterious Mori tattoo artist around the same time.

Lynn Matthews's sister was the mother of Billy James's daughter Cherie. She had attended her father's marriage as a child, as portrayed in the documentary A Daughter's Story in 1997.

Lynn was his wife when he passed away, but the history and details of Cherie's birth are not detailed.