Meredith Rodney McKay's father was a male Tau'ri, the husband of Meredith Rodney McKay's mother, the father of Dr. Meredith Rodney McKay and Jean Miller, and the maternal grandfather of Madison Miller.
He and his wife constantly argued during their son's childhood and blamed Rodney for it. They eventually divorced. (SG1: "Redemption, Part 2")
When Rodney was young, he refused to pay for a license for Rodney's dog, so the animal shelter could not track it when it ran away. (SGA: "Letters from Pegasus")
In 2004, Rodney told Doctor Carson Beckett and Lieutenant Aiden Ford that his sister was the only family that he really had, implying that both of his parents had died by then. (SGA: "Hot Zone")
In 2006, Rodney mentions to Jeannie that their father would've wanted them to be working together. (SGA: "McKay and Mrs. Miller")