A maxim in the California wine industry recommends that those seeking to make a small fortune in viticulture start with a large one. Michael Stewart, a Texas entrepreneur, fulfilled this requirement before arriving in Napa Valley. Yet the return on his vinous investments has been anything but small: The venture has brought him closer to his son, James, who has risen as president, and daughter, Caroline, who is the associate winemaker. Moreover, Stewart’s commitment to producing quality wines won him the expertise of oenologist Paul Hobbs, as well as a contract for grapes from celebrated grower Andy Beckstoffer’s Las Piedras Vineyard. Their latest dividend is the Stewart Cellars 2013 Nomad Cabernet Sauvignon ($175, stewartcellars.com), a richly extracted but balanced brew of blackberry, dark chocolate, toasted cinnamon, anise, and oak.