Guinan

Early Life
Guinan is a member of the El-Aurian species.

She was born sometime after the 1600s. She visited the planet Earth on several occasions during her youth, including in 1893, where she met the time-traveling Jean-Luc Picard. She was also on Earth in the 1990s. An adversary of Q since the 22nd century, and has remained such up until the latter half of the 2300s. 

She had returned to her home world of El-Auria by the mid-23rd century, and was among the refugees when the Borg destroyed it. Her young daughter was killed in the attack, and a despondent Guinan fled the planet aboard the freighter SS Lakul. The freighter came into contact with the Nexus, and Guinan, along with 46 others (including Yuriel Tyvan and Tolian Soran), was temporarily transported into that paradise. She was removed by rescuers from the USS Enterprise (NCC-1701-B). 

She drifted through life in the Alpha Quadrant until 2333, when, while living on an outpost on Oblivion, she met a young Jean-Luc Picard. He was able to reach out to her, and they developed a strong relationship. Years later, in 2365, she accepted his offer to live and work on the USS Enterprise (NCC-1701-D) as hostess of the Ten-Forward lounge. 

Family
In 2366, new Lt. Reginald Barclay III made such an impression on her (from his superiors, such as Geordi La Forge) that he reminded her of her uncle, Terkim. A sort of "atypical" family member, whose uncommon sense of humor influenced his niece. In four years' time, she is carried by Barclay himself into sickbay from the unbearable strain put on her special, space-time senses brought on by Trelane. Guinan's bond-sister, Delcara, chose to place herself in an infinite battle with a doomsday machine from 2367 onward. 

By 2379, she had married 23 times and had many children. 

Guinan's third husband bought her gifts every single day. He eventually died in a gardening accident. 

On the Enterprise-D
In January 2365, Picard's ship, the USS Enterprise (NCC-1701-D), picked up Guinan from Starbase 80, and she subsequently served as hostess at the Ten-Forward lounge until the ship's destruction in 2371. She befriended many of the crew, listening and giving advice. 

In the "Track A" continuity universe aboard Enterprise-D, her counterpart is a hostess by the name of Johnson*. 

On the Enterprise-E
Her whereabouts since 2371 have been mostly unknown, though as of 2374, she was living on Earth, and she attended the wedding of William Riker and Deanna Troi in 2379. (, Star Trek: Nemesis)

In 2380, at Picard's request, she briefly served as hostess of the lounge aboard the Enterprise-E during the third Borg crisis of the year. Although she admitted to a deep-seated fear of the Borg, Picard convinced her that he needed her. At the conclusion of the mission, and motivated by her belief that she could best serve her dear friend by letting him face his problems without her, she debarked from the Enterprise, but promised to visit when Picard's baby (with new wife Beverly Crusher) was born. (TNG novel: "Greater Than the Sum")

Trivia

 * Johnson is actress Whoopi Goldberg's birth surname.