According to the family tree of the Raku family included in the 'Sonyumonjo' (Sonyu's documents) which was made public for the first time in 1955, Sokei was the grandfather of Chojiro's wife.
昭和30年（1955年）に初めて公開された「宗入文書」所収の樂家系図などに依れば、長次郎の妻の祖父とされる。