Solve the riddle

Two kids are liars, three can only tell the truth. Jane:"Julia is only a liar if john is telling the truth." Julia: "If joey doesn't lie, then either Jane or john do." Joey: "Jack lies, as does Jane or Julia." John, If Julia is telling the truth, then Jane and Joey do as well." Jack: "If you round up Jane, Joey and John you will have at least one liar."