Answer by taking a quote from the following article:

Stephen Arthur Stills (born January 3, 1945) is an American singer, songwriter, and multi-instrumentalist best known for his work with Buffalo Springfield and Crosby, Stills, Nash & Young. Beginning his professional career with Buffalo Springfield, he composed one of their few hits "For What It's Worth," which became one of the most recognizable songs of the 1960s. Other notable songs he contributed to the band were "Sit Down, I Think I Love You

Stills was involved with the musician Judy Collins from 1968 to 1969 and wrote the song "Suite: Judy Blue Eyes" for her. He dated actress and singer-songwriter Nancy Priddy who was the inspiration for his Buffalo Springfield song "Pretty Girl Why". He also had a short-term relationship with Rita Coolidge, as had Graham Nash, which apparently led to the initial breakup of CSN, in 1970. During a Manassas tour in France, Stills met and married his first wife, the singer-songwriter Veronique Sanson. Their son Christopher was born in 1974. They divorced in 1979. In 1976, Stills told Rolling Stone, "My hearing has gotten to be a terrible problem. If I keep playing and touring the way I have been, I'll go deaf." In 1988, he married the Thai model Pamela Anne Jordan, with whom he had a daughter, Eleanor. His third wife is Kristen Hathaway (Kristen Stills), whom he married in 1996.  Stills's son, Justin Stills, was born in 1972 to Harriet Tunis. Justin was critically injured while snowboarding on Mt. Charleston, just outside Las Vegas, in 1997. An episode of Discovery Health's documentary series Trauma: Life in the ER featured his treatment and recovery. Another son, Henry, has been diagnosed with Asperger syndrome  and is profiled in the 2007 documentary Autism: The Musical. Stills's daughter Eleanor is a photographer and graduate of Art Center College of Design in Pasadena. Since Eleanor's graduation, she has been responsible for all recent Crosby, Stills & Nash photography. Stills has another daughter, Alex, who attends Emerson College in Boston, Massachusetts. His son Chris and daughter Jennifer are both recording artists. His youngest son, Oliver Ragland, was born in 2004 and named in honor of Neil Young, whose maternal family name is Ragland.  Like all four members of CSNY, Stills has long been involved in liberal causes and politics. In 2000, he served as a member of the Democratic credentials committee from Florida during the Democratic National Convention, and was a delegate in previous years.  The comic book series Scott Pilgrim features a character by the name of Stephen Stills, referred to as "the Talent" by the band he shares with the title character. The character also plays an acoustic guitar and sings, and is often portrayed wearing the kind of western shirts that is part of Stills's standard wardrobe. The series also has a reference to Stills's collaborator Neil Young in the character of Young Neil.

Who was his first wife?
Stills met and married his first wife, the singer-songwriter Veronique Sanson.