This is confusing for me can anyone help?

A guest was visiting mrs blake when mrs.blake's three children entered."ive never met your children", said the guest. "the middle child is bill" said the oldest child. "i'm bob" said the middle child." the middle child is bart," said the youngest child. "If you want to know who is who," said ms blake," bill always tells the truth, bob tells the truth sometimes and bart never tells the truth." identify each of the children?????