The controversy over three-parent embryos could soon be old hat. Writing in one of the world’s leading journals, one of Britain’s best-known bioethicists has outlined a strategy for creating children with four or more genetic parents. He calls it “multiplex parentingâ€.John Harris, of the University of Manchester, and two colleagues, César Palacios-González and Giuseppe Testa contend in the Journal of Medical Ethics (free online) that this is one of many exciting consequences of using stem cells to create synthetic eggs and sperm. (Or as they prefer to call them, in vitro generated gametes (IVG).)After the discovery of induced pluripotent stem...