Joseph, father of Ethan Allen had siblings but no David according to my records. His siblings were as follows in order of birth: Nehemiah d. young, Mercy b. 1695, Nehemiah b. 1697, Mary b. 1699, Daniel b. 1701, Hester b. 1704 d. 1706, Lydia b. 1706, Hester b. 1707, Joseph b. 1708 (father of Ethan), Ebenezer b. 1711 and Lucy b. ? d. prior to 1728. None of these children had a son named Adonirum. This does not support what you suggest, but it is what I have...Unless there was another brother not noted in my "Allen Memorial Book". If I can be of further help, please feel free to contact me.