My family come from Armagh , Heath Hall, I know of was the family home, and, yes, there is some association with Marmaduke Whitchurch though exactly what I'm not sure. I'm sure it was important to the family as I, unfortunately, have inherited it as a family name , Nigel Gordon Whitchurch Seaver) . There is also a book "The history of the Seaver Family" by George Seaver which is out of print (to put it mildly) but you may be able to borrow one, which details the family trees of the seavers of heath hall.
My Grandfather was brigadier Charles Douglas Kingsley SEAVER RAMC who had three sons LLoyd "Pat" and Gordon who was my father, Dr Richard Gordon Seaver born Peshawar 1920.
He had four sons Richard P K , Michael, myself and Jonathan (d).