Which of the six key characters on the U.S. TV show "Friends" was the only one without any sibling?

On the U.S. 1994 to 2004 NBC TV sitcom "Friends", the only key character of the six individuals without any sibling was Chandler Bing. He was portrayed by Matthew Perry. He was an only child who was apparently from an affluent family.

Regarding the other characters, Rachel Green (Jennifer Aniston) was born to Leonard and Sandra Green, who gave her and her two sisters Jill and Amy, a rather spoiled upbringing. Next, Phoebe Buffay (Lisa Kudrow) was an identical twin with her "evil" sister named Ursula. They lived in uptown New York with their mother, until she committed suicide. Third, there was Joey Tribbiani (Matt LeBlanc). He came from a family of eight children, where he was the only male. He had seven sisters: Gina, Tina, Dina, Mary-Angela, Mary-Therese, Veronica and Cookie.

The two remaining key people are Ross Geller (David Schwimmer) and Monica Geller (Courteney Cox). Ross is Monica's brother, and he was a year older than her. They had some of the same friends in high school, like Rachel.

During this series, the friends lived in the same apartment complex. They faced life and love in New York City. They would stick their noses into one another's business and would swap romantic partners, which always led to the kind of disturbances that average people would normally never experience.