Ambalika was the daughter of Kashya, the King of Kashi

Varanasi

-Etymology:The name Varanasi has its origin possibly from the names of the two rivers Varuna and Assi, for the old city lies in the north shores of the Ganga bounded by its two tributaries, the Varuna and the Asi, with the Ganges being to its south...

 and queen of Vichitravirya

Vichitravirya

Vichitravirya in the Hindu epic Mahabharata is the younger son of queen Satyavatī and king Śaṅtanu. His elder brother, Chitrāngada, had initially succeeded their father to the throne of Hastinapura, but when he died childless, Vichitravirya succeeded him.Vichitravirya was still a child when he was...

, King of Hastinapura

Hastinapura

Hastinapur is a town and a nagar panchayat in Meerut district in the Indian state of Uttar Pradesh.-History:Hastinapur was the capital of the kingdom of the Kauravas, belonging to the Kuru dynasty of kings. The throne of this city was the prize over which the Kurukshetra War of the epic...

.

Along with her sisters Amba and Ambika, she was taken by force by Bhishma

Bhishma

Bhishma or Bheeshma or Devavrata or 'Bhishma Pitamah' was the eighth son of Kuru King Shantanu who was blessed with wish-long life and had sworn to serve the ruling Kuru king. He was one of the most prominent characters of the great Indian epic, the Mahabharata. He was the grand uncle of both the...

 from their Swayamvara

Swayamvara

Swayamvara , in ancient India, was a practice of choosing a husband, from among a list of suitors, by a girl of marriageable age. Swayam in Sanskrit means self and vara means choice or desire ....

, the latter having challenged and defeated the assembled royalty. He presented them to Satyavati

Satyavati

Satyavati was the queen of the Kuru king Shantanu of Hastinapur and the great-grandmother of the Pandava and Kaurava princes . She is also the mother of the seer Vyasa, author of the epic...

 for marriage to Vichitravirya.

After Vichitravirya's death, his mother Satyavati sent for her first born, Rishi

Rishi

Rishi denotes the composers of Vedic hymns. However, according to post-Vedic tradition, the rishi is a "seer" to whom the Vedas were "originally revealed" through states of higher consciousness. The rishis were prominent when Vedic Hinduism took shape, as far back as some three thousand years...

 Veda Vyasa

Vyasa

Vyasa is a central and revered figure in most Hindu traditions. He is also sometimes called Veda Vyasa , or Krishna Dvaipayana...

. Veda Vyasa had come from years of Great Tapas and as a result of his askesis, he looked tremendously unkempt. He volunteered to come after a year of cleansing but Sathyavathi was desperate having lost both of her son without heirs and her stepson disagreed to break his celibacy. She did not wait, Veda Vyasa was to impregnate Ambika she closed her eyes fearing Veda Vyasa's looks so Veda Vyasa predicted a blind child (Dhritarashtra) will be born to her. So Sathyavathi asked to sow the seed in Ambalika the widow of Vichitravirya again Ambalika was told to resist from closing the eyes but her body turned pale looking at Veda Vyasa so Pandu with pale body was born to her.