Ramirez had been sought for questioning in the deaths of a 1-year-old boy and a 48-year-woman. A 2-year-old girl who also was stabbed was in stable condition at a San Jose hospital.
While not calling Ramirez a suspect in the killings, Hirokawa said there were "no other persons of interest at this time."
Relatives said Ramirez was the children's uncle and their grandmother was his mother. He lived at the home and had a history of mental illness.
The stabbings were discovered about 3:30 p.m. Wednesday when a family member came to the home in unincorporated Santa Clara County.