I just saw your post today and might be able to help you out.My wife is the one with the Bainbridge lineage.In short, my wife is related to the William A. Bainbridge, born 1692, as follows:
John Bainbridge and Sarah Clows, both born in England and married in Pennsylvania, had two boys
John A. Bainbridge, born about 1692 and
Edmund Bainbridge, born about 1693.
My wife is from the John A. lineage.
Commodore William B. Bainbridge is from the Edmund lineage.
I believe your William B. Bainbridge is from the John A. lineage, too.
John A. Bainbridge had four sons:
1. John Bainbridge III, born about 1714, died about 1787,
married first to Sarah Daughty, 1-24-1740, and second to
Mary (mentioned in his Will dated 1784.His children
mentioned in his Will are John (IV), Edmond, Charles,
Sally (perhaps a nickname for Sarah), Fanny (perhaps a
nickname for Frances), Betsey, David, Polly Tucker,
Lucia, and William.I believe, but have been unable to
confirm, that the first two sons, John IV and Edmond,
were by wife Sarah Daughty, and the remainder of the
children were born to Mary, the second wife.See more
2. Theophilus Bainbridge, born about 1722, died 8-30-1773,
no wife no kids;
3. Edmund Bainbridge, born after 1722, died before 1761, no
mention of wife or children; and
4. William Bainbridge, born 7-11-1740, died 5-4-1819,
children were Timothy (10-30-1778), Sarah (4-7-1782);
Claricy (2-14-1786), and Mary (7-5-1795).
I have copies of the actual Wills from John I, John II, and John III.I have a copy of a land deed from John (I believe the IV) and his wife Ann deeding part of the Bainbridge farm near Jacob's Creek in Hunterdon County in 1793 to William Bainbridge (#4 above, born 7-11-1740), who if I'm right, is John IV's uncle, even though they were born about the same year.This William also owned farm land on or near Jacob's Creek.And another interesting fact is that John IV, whom I believe was born about 1740, the year his parents were married (1-24-1740) served in the same New Jersey Company #3 during the American Revolutionary War as William Bainbridge born 7-11-1740 (this according to Rycker's Officers and Men of new Jersey, 1872, page 495.)
Now to your William B.The 1850 U.S. Census shows a William B. Bainbridge born about 1772 in New Jersey living in Marion County, Virginia.Going back to John III's Will written in 1784, he specifically mentions that his daughters Sally, Fanny, and Betsey are minors.At that time the age of majority was 18 years, so these girls were born after 1766.He also mentions that Polly is married with a last name of Tucker.Fanny later married Daniel Lanning in 1795, who was born in 1773.That puts Fanny being born, on average, twenty years before she married and at least no older than her husband, so that she was probably born in 1773 to 1775.
So, although I have no direct evidence that William B. Bainbridge is John III's son, I think he is, especially looking at the ages of his brothers and sisters and the fact that he was born in New Jersy according to the U.S Census facts.
Now the reason this is important in my research is that I traced my wife's Bainbridge connection back to Theopilus Bainbridge, born 11-16-1777.I have not been able to find his parents, except that the only Bainbridges in Hunderton County, New Jersey that fit the chronoligical possibility of being his father are John IV or his brother Edmond.
I hope this helps you, and I will be happy to send you pdf files on what I have if you contact me directly at firstname.lastname@example.org.If you can fill in any of my blanks, I would appreciate that as well.