Yes - we're researching the same family. I never knew what happened to Sarah Pelton Simmons (dau of David P & Hannah Way Simmons) - maybe we could share? Sarah would have been Seth's (my g-g-grandfather) sister.
My research agrees with yours - their father, David Pelton Simmons (1801-1872) was married to Hannah Way (1801-1868). I have a lot more on the Way family. David P & Hannah had the following children:
Sarah Pelton Simmons, b 1824 in Hanover, NH
Samuel Way Simmons, b 1827 in Hanover, NH, d 1864 in VA
David Bradley (DB) Simmons, b 1829 in NH, d 1906 in NE
Seth Simmons, b 1832 in VT, d 1885 in NY
Harriet Simmons Green, b 1835 in NH, d 1918 in NY
Josiah Simmons, b 1838, d 1862 in NY
Mary E Simmons Calkins, b 1842, d 1933 in NY (I still need documentation for her death)
I'm currently working on this family line (David & his father Samuel, etc) and would like to correspond with you to share information. Please contact me at firstname.lastname@example.org
Looking forward to hearing from you.