As with any genealogical endeavor, there are conflicts from generation to generation and frequently a major effort in coming up with the necessary documentation to prove the line with a "reasonably exhaustive search."
Thanks to scouring available family trees, I have already come up with six sources to check.
Now the dream collection of documents would be Virginia deeds that would confirm the line.
Francis Land, the immigrant, named his sons, Renatus and Francis, in his will of 15 April 1654. This according to several trees. [Need to see the will!]
Hopefully, an examination of Renatus' probate will name his son Robert. Robert's wlll name son Edward, Edward's will name son Thomas and Thomas will name son John.
Hopefully, as well, all of these will exist!