What is the relationship between Wang Xianzhi and Wang Xizhi?

Father-son relationship.

Wang Xizhi (321-379, or 303-361), also known as Yishao and Danzhai, was originally from Linyi, Langya (now Shandong), and later moved to Shanyin (now Shaoxing, Zhejiang). General Zhiyoujun, internal historian of Kuaiji, was a great calligrapher in the Eastern Jin Dynasty and was revered as a sage of calligraphy by later generations.

Wang Xianzhi (344-386), a calligrapher of the Eastern Jin Dynasty, was born in Shanyin, Kuaiji (now Shaoxing, Zhejiang). When he reached Zhongshu Ling, he was called Dalling in his old life, and he was the seventh son of Xi. He learned calligraphy from his father when he was young. Later, he adopted Zhang Zhi's method, created new methods and created his own style. He was as famous as his father and was known as the "Two Kings". His calligraphy is exquisite in regular script, running script, cursive script, and official script. He is especially famous for his calligraphy in script script.