Complex sentence: Realty, or heritable property, was originally inherited in joint tenancy, termed gavelkind, passed on to the kin group as a whole, but after the household became the focus in the late Middle Ages, only to the deceased's surviving sons.
Split into simpler sentences: Realty, or heritable property, on the other hand, was originally inherited in joint tenancy, termed gavelkind, and passed on to the kin group as a whole. However, after the household superseded the kin group in importance in the late Middle Ages, preference was given to the deceased's immediate family, specifically any surviving sons.