What do we know about mr.irby’s grandfather

Gunnar Irby is Jacqueline's grandfather, the father of Mary Ann Irby, but the children call him "Daddy." Of all Mary Ann's children, Jacqueline is closest to Gunnar. Gunnar believes in nature and farming, and he does not share Georgiana's religious faith. When he dies, presumably of lung cancer, Jacqueline is devastated.