Who is Lord Holster from A Storm of Swords and what is their importance?

Lord Holster is Catelyn, Lysa, and Edmure's father. He is the Lord of the castle, Riverrun. In this novel, Holster is on his deathbed, and then does die. Edmure, as his son and heir is expected to shoot an arrow to light the funeral pyre, as it drifts in the water. Edmure, however, cannot make the shot, and so his uncle, The Blackfish, takes the shot. Blackfish and Holster had been estranged for many years, but right before Holster's death, they make amends. Holster's favorite child had always been Catelyn.