Two Kids are Liars Brain Teaser

Two kids are liars, three can only say 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 of Julia."

John: "If Julia is telling the truth, then Jane or Joey do as well."

Jack: "If you round up Jane, Joey and John, you will have at least one liar."

The compulsive liars are?