Father's uncle-in-law could be called uncle.
Uncle's father could be addressed as his biological grandfather or grandmother, or he could directly address them as grandfather or grandmother. However, in some areas, people would address the man according to his seniority. The father of the uncle would be called grandaunt. In general, one could decide how to address his uncle's father according to personal habits and regional customs.
Your uncle's daughter should be called a cousin.
Uncle's daughter is my cousin. According to document [2], I can call her aunt or cousin. Therefore, my child can call uncle's daughter aunt or cousin aunt.
Your son can call your uncle "son-in-law".
His father was called the Heavenly Ancestor. Gaozu's father was called the Heavenly Ancestor. According to the records in Er Ya, the one who gave birth to him was his parents, the father of his father was his grandfather, the father of his grandfather was his great-grandfather, the father of his great-grandfather was his great-grandfather, and the father of his great-grandfather was his great-grandfather. Thus, the title of the great-great-grandfather's father was Heavenly Ancestor.
His great-grandfather's father called him Tianzu. According to the explanation of Er Ya, the father of Gaozu was called Tianzu.
His great-grandfather's father called him Tianzu. According to the explanation of Er Ya, the father of Gaozu was called Tianzu.
The child of the sister-in-law's father could be addressed as a cousin, depending on his age.
His great-great-grandfather's father was called the Heavenly Ancestor.