Yokosuka Domain
Toshinaga was the 6th son of Honda Tadatoshi, daimyō of Okazaki Domain. His mother was a daughter of Inoue Masanari, daimyō of Yokosuka Domain. Toshinaga succeeded to clan leadership upon his father's death in 1645; however, he received only 50,000 of the 60,000 "koku" that had comprised Okazaki Domain under Tadatoshi's rule; the remaining 10,000 "koku" was divided between his brothers Honda Sukehisa and Honda Toshirō.