My great, great grandfather was Lyman M. Chaffee 1814-1887. He did have a sister Amanda.
Their mother was Grace (Whipple) Chaffee, Jr. She was bore 1790 in Vermont, USA and
died in 1836. Grace's parents were Ethan Whipple and Abigal (Hawkins) Whipple.
I have the same info. that you have for Amanda Chaffee.