Liu Dehai and Hai Hongmei's matrimonial bed is laid with a thick quilt embroidered with the characters for "double happiness," words meant to augur good fortune for just-married Chinese couples. This should be a room of joy and hope, but Liu's mother doesn't want anyone investigating too closely. "Please," she says, "do not speak of this room." The marriage of Liu and Hai is a subject of shame, for they are not just husband and wife; they are also first cousins.
Their marriage, and others of cousins and even siblings, is the latest consequence of China's profound shortage of females. For...