Who is Geert von Innstetten from Effi Briest and what is their importance?

Geert is the thirty-eight-year-old aristocrat, who marries Effi Breist, a much younger woman. Ironically, the love of his wife was Effi's mother, who chose to marry another man. Geert is a compassionate, fatherly husband, but he has no real love for his wife.