Karan Singh was born in Cannes, France into the Dogra dynasty. He was the only son of Maharaja Hari Singh, the ruling Maharaja of Kingdom of Jammu and Kashmir. His mother, Maharani Tara Devi, who was the fourth wife of his father, was the daughter of a landowning Katoch Rajput family and came from Bijapur (Vijaypur near Bilaspur) in Kangra district of Himachal Pradesh.[dubious – discuss][citation needed]

Singh was educated at Doon School, Dehra Dun, a boarding school, which represented a departure from the usual practise of princes being educated by tutors at home. The school was very elite, but it nevertheless meant that Karan Singh shared the classroom (though not the hostel) with boys from non-royal backgrounds, and received a standard education. Unusually for the scion of an Indian royal family, he then enrolled in a college for a graduate degree, receiving first a B.A. degree from Jammu and Kashmir University, Srinagar, and subsequently an M.A. degree in Political Science and a PhD degree from University of Delhi.

In 1950, the 19-year-old Karan Singh was married to 13-year-old Yasho Rajya Lakshmi, daughter of a nobleman belonging to the Rana family of Nepal. Her father, General Sharada Shumsher Jung Bahadur Rana, was a senior army officer and the son of Mohan Shumsher Jang Bahadur Rana, the last Rana Prime Minister of Nepal.The match, arranged by their families in the usual Indian way, was entirely harmonious and lasted all their lives. The couple had three children:

Yuvraj Vikramaditya Singh, elder son and crown prince; married Chitrangada Scindia, the daughter of Madhavrao Scindia of Gwalior, in 1987.
Ajatshatru Singh, second son; took to politics, was elected to the state assembly from the Nagrota constituency and became a minister in the state government. His wife is the daughter of an army officer.
Jyotsna Singh, only daughter, married into a chauhan family belonging to Mainpuri in Uttar Pradesh.