Some of the nation’s largest child-product companies, including Johnson & Johnson, Proctor and Gamble and Kimberly Clark, are the target of a nationwide class-action lawsuit by parents after a study revealed that many of the companies’ products contain questionable chemicals. The suit, filed March 19 in U.S. District Court in Chicago, will represent parents or other consumers who purchased any of an extensive list of products, if the court certifies the action, according to l...