Aghadowey explored the possible "Dobbin" connection in Armagh where the name was turning up but nothing conclusive for Leonard Barrett.
Thank you Aghadowey for spending time going though the thread, over 95 pages, it was very much appreciated.
Quite probably it is true that his father had passed away in 1840 although no documentation to be positive regarding that.
Captain Leonard Barrett was given the schooner Mariquita in 1860 for a trip New York to Africa. This schooner may have been used in the slave trade.

He was very young at 19 years 9 months
(again no source given)
This is the quote from ancestry tree " Took charge of schooner, Mariquita. He was paid $80 a month and was directed to sail to Africa and back to New York. At this time Captain Barrett was 19 years 9 months old" Same tree owner also names the first born daughter - Mariquita Georgina Barrett (1861) - although you can see on the 1880 census it was Margaret by then.
Tending to think this has come from a descendant as was the "Stowaway" story.
Perhaps worth an enquiry to ask ? We have been lucky to find a volume of information on Leonard Barrett, the Rutledge family (from where both his wives came) and other descendants.
The original poster has been on line since you joined SBDJ, have you tried to contact him through the personal message system. He was working for a friend who was a very elderly lady back in 2011 and I believe he may have been in contact with a family tree member. So he might have more answers for you.
Another part which caught my eye after several read thru's was reply 32 when Fred said that his friend had corrected herself and thought there may be a link to James Buchanan 1791 - 1868 (not William Harrison) 15th President of the United States, U.S. Congressman, Senator, Diplomat.
He never married, so the link would have had to be from one of his siblings. Quick look though those did not turn anything up to link Buchanan to Barrett. Thousands of anc trees on that family
https://en.wikipedia.org/wiki/James_BuchananThere was a marriage in 1826 of a John Barrett to a Jane Buchannon in Armagh. Ireland. Again nothing to connect Leonard Barrett to them.
https://www.familysearch.org/ark:/61903/1:1:WG72-HBN2Sandra