Zajíc was the son of unknown parents. The date and place of his birth have not been found.
He had two marriages/partners. His first wife was Katharina z Častolovic, who he married in 1447. The place has not been found. They had no known children.
His second wife was Anna von Troppau-Leobschütz. They were married, but the date and place have not been found. They had no known children.