Subhadra is the only daughter of Vasudeva, born to him by his wife Rohini Devi. She is born after Krishna rescues thier father, Vasudeva, from prison and is thus much younger than both her brothers. Subhadra therefore grows up in comfort as the princess, and escapes the travails that haunted her family before her birth.
Arjuna, the Pandava, once spends 1 year in exile for breaking a vow. He spends the last portion of this exile in Dwaraka, at the residence of his cousins Krishna, Balarama and Subhadra. They are his cousins because their father, Vasudeva, was the brother of Arjuna's mother Kunti. During his sojourn at Dwaraka, a romance ensues between Arjuna and Subhadra. This matter was abetted by Krishna, who had always been particularly attached to Arjuna, and wished nothing but the best for his sister Subhadra.
As the period of Arjuna's exile draws to a close, and his departure homeward becomes imminent, Arjuna proposes marriage to his cousin, and she acquiesces. Knowing that the entire family would view with disfavour the prospect of Subhadra becoming the fourth wife of her much-married cousin Arjuna, Krishna facilitates the elopement of the couple and their departure for Indraprastha. He gives the couple a crucial piece of advice related to their elopement: it was Subhadra, and not Arjuna, who drove the chariot away from Dwaraka and towards Indraprastha. Krishna later uses this fact to persuade his family that Subhadra had not been abducted; on the contrary, it was she who had kidnapped Arjuna!!
Subhadra and Arjuna soon have a son, the valiant Abhimanyu. Not long afterwards, the celebrated game of dice ensues between the Pandavas and the Kauravas. The Pandavas leave Indraprastha to spend 13 years in exile. It is decided that Subhadra and her infant son must spend the period of exile in Dwaraka, so that Abhimanyu may profit from receiving Krishna's tutelage and gain a suitable education, that would prepare him for the struggles and responsibilities that he, Abhimanyu, is expected to bear in later life.
At the end of the period of exile, Arjuna sends for his wife and son. Abhimanyu is wed to Uttara, daughter of king Virata. To Subhadra's great grief, the young Abhimanyu is killed during the Kurukshetra war which ensues soon afterwards. Uttara is pregnant at that time and is later delivered of a son, who is named Parikshita.
Parikshita is destined to become the sole surviving dynast of the entire Kuru dynasty, Pandavas and Kauravas combined. When he comes of age, the Pandavas (being his grandfather Arjuna and four grand-uncles) anoint him king of their realm and retire to the Himalayas. Subhadra remains behind to guide and mentor her grandson.