Your Thaddeus was son of Elijah and Persis Houghton Allen who were married in Guilford Twp., Windham Cty., VT (near Brattleboro) on 18 Aug 1799.I found the marriage material in the Vital Records of VT -- I can try to send you a copy, but it's not very legible and really doesn't contain much information.I believe the entry is on the LDS microfiche, but I can't remember for sure.
Both Elijah and Persis are buried in the Town of Clayton's Three Mile Creek Cemetery in Jefferson County, N. Y.You may see their stone by going to my website and looking under Cemeteries.http://freepages.genealogy.rootsweb.com/~twigs2000http://freepages.genealogy.rootsweb.com/~twigs2000
I know several researchers who might help you more -- one is a descendant of Mary Ann Otis.
I'll write you personally.I would dearly love to have your lineage from Elijah for my database.Looks like your Amasa's wife was Rhoda Greenleaf Quiett.Do you have a date in 1947 when your Amasa died, Patricia?
Oh, Thaddeus was probably born in VT or maybe Herkimer Co., N. Y.Do you know?He first married Lucy Clark and she is also buried at Three Mile Creek Cemetery.