Jerry, I have a number of items reagrding the Jenison family.
I am researching for my nephew (inlaw) who is a direct descendant of Robert Jennison, b. 1607, d. 1690. His line comes down from Robert's second marriage to Grace (Lnu?).His ancestry line is through Elias Jennison (1724) and Hannah Twiss (abt. 1726).It looks as if you ancestor Martha Twiss is a sister to his Hannah Twiss.
I show Peter, Sr. having two sons, one is Peter, Jr. the other "Orange Twiss Jennison", is that correct?
You mentioned Daniel Ambrose Jennison and family all dying in Carthage, Missouri.I go through Carthage, MO quite often and would be glad to do any research or take pictures, etc.Do you know where the family would be buried?