I stumbled across your forum and was amazed at the number of Kniffins/Kniffens out there. I have only met one other Kniffin other than my family in all my life.
I am a Kniffin through adoption by my stepfather, William Boone Kniffin who was born in Miami in 1934 (I think.) His father was Walter D. Kniffin whom I never met as he died in WWII. Williams mother was Mary Boone (I understood of the Daniel Boone family). He has a sister named Mary.
I have a twin brother Andrew C. Kniffin and also a half sister Valerie and half brother Walter D. Kniffin both who are children of William B. Kniffin and Sarah D. Craig.
If there is anyone who wants additional information on this line of Kniffins I could try to find out more as well as get the correct names and birthdates. This Kniffin family was well established in the Miami Springs, Florida area at least by 1925 as Kniffin Transfer Company was founded then.