Is “In official history, Yin Kaishan was a famous general of the early Tang Dynasty, unrelated to Xuanzang's family background” true?

In the official history "Old Book of Tang", Yin Kaishan was a renowned founding general of the Tang Dynasty. However, in Chapter 009 of "Journey to the West", he is depicted as the prime minister of the current dynasty and the maternal grandfather of Tang Sanzang, having led troops to Jiangzhou to suppress water bandits. Original text: "殷开山丞相家，是你母生身之父母。" ("Journey to the West", Chapter 009)