Who is Mother Robert, Father Robert, Roberta I and Roberta II from Four Plays and what is their importance?

Mother Robert, Father Robert, Roberta I and Roberta II are an embodiment of convention. The playwright is suggesting that attempting to control existence is in fact something grotesque, misshapen and monstrous. The physicality of the Robertas, the way she seduces Jack into marriage, and especially the descriptions of her final appearance on stage all suggest that Jack is corrupting an independent, chaotic personal existence into something expected, and therefore quite disgusting. The thematic implication is that any attempt to impose order on chaos is essentially a distortion of true, chaotic, absurd identity.