Looking on national archives site, there is a will for Elizabeth Hodder, mother of John, who died in 1846 aged 77. She names her son John as the eldest, plus another 2 sons Servington and William, daughters Eliza married to a Widdicombe, Mary married to a Wroth, and daughter Jane single. Also mentioned are the granchildren, children of John, Named as Ann, Jane Eliza, John and Catherine.
She is buried at Ugborough with a Servington (no date of burial recorded for them, but daughter Catherine who died 1842 is recorded.

According to the Ugborough burial ground site there is another Servington born 1763 died 1835 in another grave with a Jane born 1806 died 1887, so could be the son Servington buried with his mother and sister, and father Servington buried with his daughter.
This was quite a well to do family looking at the with investments, and cash quoted, very difficult to read. Will available on National archives site if you register, and go through the process of purchasing, for free, then you can download.
I had thought that the name Maddox would have flung up more information but have not come across it....yet!