The following is a page from the manifest of the Schooner Horatio:

 

Name:	Andrew Ralston
Sex:	Male
Age:	22
Immigration Date:	1820
Immigration Place:	Philadelphia, Pennsylvania, United States
Birth Year (Estimated):	1798
Birthplace:	Great Britain
Ship Name:	Horatio
Source:	National Archives and Records Administration
Name:	L Ralston
Sex:	Male
Age:	29
Immigration Date:	1820
Immigration Place:	Philadelphia, Pennsylvania, United States
Birth Year (Estimated):	1791
Birthplace:	Great Britain
Ship Name:	Horatio
Source:	National Archives and Records Administration

 

Per the records, Andrew and “L” accompanied each other.  The ages of Andrew and “L” Ralston (22 and 29) fit perfectly with later census records which show Andrew born c1798.  There is an error on the manifest in that it does not list “L” as being female, but only shows a “do” or ditto of the above entry. Otherwise, all other information fits the information passed down in the family regarding the arrival of Andrew and Loveagh.

Regarding "L. Ralston" being listed as "Male", it is my theory that the clerk entering the names was unfamiliar with the name "Loveagh" and just put down an "L".  (Note all the other entries, except for "Mrs.", used the full name.  I think the other information was added later and the gender of "L. Ralston" was not apparent, so the "Male" was dittoed.

The Schooner Horatio was too small a vessel to have made the trip from Ireland, so Andrew and Loveagh probably were on a different ship for that part of the journey.

A schooner similar in size to the Horatio

It was not uncommon for Irish immigrants at that time to sail to New Brunswick before a final leg to the U. S.  In a paper by Brian Mitchell, "Londonderry to Canada, the 'Cheapest and Shortest Sea Passage' to North America", he says that the cheapest way at that time to get from Ireland to the U. S. was by way of Canada. He quotes Thomas Mellon describing how in 1818 his family sailed from Derry, via Canada, to the US.  It took twelve weeks to get to St. Johns and another two weeks to get to Baltimore. (They were headed to Pittsburgh, so went overland from Baltimore.)  According to Mitchell, prior to the 1860s railway network, the port at Derry served as the emigration port for Counties Derry, Donegal, and Tyrone.