Yoshimasu was the 2nd son of Itô Yoshisuke. An elder brother had died at a young age and so Yoshimasu was designated as Yoshisuke's successor. However, in 1569, he fell ill while on campaign against the Shimazu clan and died.
References
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005