Later on in the decade, he would have another brother, Hōjō Tokifusa, and a sister whose name remains unknown, but their birth dates are not known.

Yoshitoki was from the first day of his life expected to succeed his father as the head of the Hōjō clan in Izu.

That same year, a disgruntled Prince Mochihito, a son of Go-Shirakawa, grew weary of the Taira leadership, believing he was denied the throne just so his young nephew, Emperor Antoku, who was half Taira, could be enthroned.

Yoritomo responded readily, and Yoshitoki, Masako, Tokimasa, and the entire Hōjō clan supported him.

Yoritomo created his base east of Izu in Kamakura, located in Sagami Province.

In 1183, Yoritomo's rival and cousin, Minamoto no Yoshinaka, entered Kyoto and drove out the Heike (and the young Emperor Antoku).

That year, Hōjō Tokimasa received from Cloistered Emperor Go-Shirakawa the first appointments for jitō and shugo, or constable and steward.

In 1192, cloistered emperor Go-Shirakawa (who died later that year) bestowed upon Yoritomo the title of shōgun.

Yoriie, out of support, abdicated in 1203, went to live in Izu, and was executed on Tokimasa's orders in 1204.

During this period, a certain Hatakeyama Shigetada, Yoshitoki's brother in law who had married his sister (not Masako) was executed by Tokimasa's men, on false charges of treason.

When there were plans to have Sanetomo executed also, Masako and Yoshitoki ordered their father to abdicate or they would rebel.

In 1218, Regent Yoshitoki sent Masako to Kyoto to ask the now Cloistered Emperor Go-Toba if one of his sons, Prince Nagahito, could become Shogun Sanetomo's heir, since he had no children.

Cloistered emperor Go-Toba, disillusioned with the Hōjō, declared Regent Yoshitoki an outlaw and wanted him executed.

He was succeeded by his son and heir, Hōjō Yasutoki, as the third Shikken for Shogun Yoritsune.