Number of boys

The Find-a-Grave site for John Wallace (~1750) makes some interesting claims. Remember that he is a key figure in the genealogy I am working on, and undoubtedly my great-great-great-great grandfather.

This site claims that there were four brothers and that they emigrated in 1770; furthermore they landed in Carlisle Pennsylvania. John had a son there but went back to Northern Ireland, leaving the son to be raised by grandparents (this part has been backed up by other sites). Of the three brothers, Hugh went to South Carolina, James stuck around Philadelphia and eastern PA, and William went to Goshen, NY. The son, William, after growing up in Carlisle (not sure about this), became father to many of what is known as the Carlisle Wallaces.

Let's back up a little. If four emigrated from Northern Ireland, is it possible that the pig-stealing boys met up with them in Northern Ireland before leaving? If so, the original legend (2 boys stole a pig in Scotland, made it to No. Ireland, stopped over, emigrated to PA) could be true that way. It could be that the number 3 appeared as a compromise between the two truths - there were two at one end, four at the other.

At the moment John (~1750) has the only even approximate birth date. But if we know they emigrated in 1770, or we assume that it's true (there is no source on this information), we can make a lot of inferences. Perhaps we can start from there. Where and how can we find these elusive characters? Fortunately I have ancestry.com again. Start there, perhaps.