Who is Commander Roderick Blaine from The Mote in God's Eye and what is their importance?

Commander Roderick Blaine is one of the main characters in the story. He is the third son of the Marquis of Crucis and seeks his future in the Navy. He enters the military knowing he won't ever hold the family title as he has two older brothers. Rod enjoys the military and looks forward to developing his career. He is shocked when both brothers are killed and Rod becomes next in line for the Crucis title. His father, still alive, is a powerful man politically and the family is extremely wealthy.