Mr. Barkis is a cart-driver who brings David from his home village of Blunderstone, Suffolk, to Yarmouth, where the Peggottys live. Yarmouth is also David's gateway to London and the larger world, so David travels in Mr. Barkis's cart quite often once he starts school. Mr. Barkis develops marital designs on Peggotty because he knows that she makes amazing apple pastries (which we guess is...not the worst reason to want to marry someone). So he makes David carry a message to Peggotty: "Barkis is willin'" (5.33). This message makes Peggotty laugh herself half to death. Still, once Mrs. Copperfield dies and the Murdstones turn Peggotty out of the house, she decides it wouldn't be such a bad thing to marry Mr. Barkis.
the son of his beloved but now dead sister , is his only living relative , and also the only person who want to pull him out of isolation and back into the world.