From research I've done on the Chapman, Welles, Hurlbut, Churchill and Hodge connections to Mary Deming, d John Deming and Honor Treat, I've found early Demings mentioned in many early Connecticut Family histories. The one that seems to hold hints/answers for your question is "John Deming and Honor Treat Family", It says (with sufficient documentation!) that John Deming Jr was the son of John Deming and an unknown spouse. Jonathan was his son by Honor Treat (1615-1705). Jonathan's siblings included: Sarah Deming Moody; Hannah Deming Buckley; Rachel Deming Morgan; Samuel Deming m Sarah Buck, who married [2] Benjamin Churchill; Ebenezer m Sarah; David Deming m Mary; Mary Deming Hurlbut [Hurlbut, White, Churchill, Hodge.Three generations later, Benjamin Hodge married Sarah Churchill — Kissing cousins?; Mercy Deming (1) Curtis (2) Joseph Wright.
Under "Further Deming Family Connections": Elizabeth stated in her 1678 will, "my beloved brother Mr. John Deming sen," as noted in an earlier reply. John Deming was appointed a supervisor of Thomas Welles's will and took inventory of same. Elizabeth was most likely John's half sister.