I'm researching General John Sullivan and need to know what his sons, John (1767-1819) and James (1768-1796) did for a living and how they died. I've looked and looked and only found birth and death dates as far as information on them.
We can start with an article in the October 1865 NEHGR which confirms the dates you give in the question:
This does give a little more information, mainly that John died in Baton Rouge. Adding that to a search query brings up another source, General Catalogue of the Officers and Students of the Phillips Exeter Academy, we find all three brothers listed, with occupations: Lawyer, Lawyer, Lawyer.
Since the other birth and death information matches the earlier genealogical record, we have a pretty good match.
(Note that since both John and James are listed as having died s.p. or sine prole, meaning without issue, you wont be finding any descendants from these two.)