What is the relationship between Xue Dingshan and Bi Guiren?

It's Xue's son.

Bi Lizi (614-March 24th, 683) was born in Longmenxiu Village, Jiangzhou, Shanxi Province (now Hejinxiu Village, Shanxi Province), and was a famous strategist and politician in the Tang Dynasty. Great achievements have been made in the military and political fields, such as "a good strategy to stop the war", "three arrows to determine the Tianshan Mountains", "bravely recovering Liaodong", "benevolent governance of Koguryo", "loving the people for the city" and "taking off your hat to repel ten thousand enemies". After 30 years of hard work, Li Xue was born in Longmen, Jiangzhou, Shanxi Province in the ninth year of her career (6 14). He is a descendant of Xue Andou, a famous soldier in the Northern and Southern Dynasties, and belongs to the Xue family in Hedong, but his father Xue Gui died young. Although he was poor since childhood, he studied literature and practiced martial arts, and worked hard, so he was born with extraordinary strength. But he was born in chaos. When he was 30 years old, the records described him as poor and frustrated, hoping to move his ancestral grave in order to bring good luck. His wife said, "A capable person should be good at seizing opportunities. Now the emperor uses his personal expedition to Liaodong, which is the time when you need a valiant soldier. You have this ability, why don't you join the army and make a name for yourself? It's not too late to bury your parents when you have money to return to China! " Hearing this, Gui Ren felt reasonable, so he bid farewell to his wife, went to Xinjiang to find General Zhang Shigui, enlisted in the army, and began his legendary experience of galloping on the battlefield for 40 years. Xue Dingshan Guodingshan

Xue's son married, led the army to pacify Xiliang, and was later killed by Wu Zetian.