In the 1831 Census for Aghanloo/Drumaderry: you will also find Thomas Crawford.
Thomas Crawford was my ancestor: he was b. 1809 and married Mary Martin....they moved to Canada in 1840. He listed himself as a METHODIST farmer: not Presbyterian.
I would guess that Thomas and William Crawford Sr. were likely brothers: or at least cousins.
By the time you get to the 1853 Griffiths report:
Robert of Anghanloo Drumaderry still living there
William living in Ballyhanna: along the Aghanloo Road nearby
Both are fairly close to Limavady.
Bear in mind these names: Drumaerry and Ballyhanna are Townsland names: originally the name of a spot or homestead just big enough for one family.
So this Robert is living at the homestead of the land my Thomas was head of in 1831......
So clearly they are related.......we dont know if this is by then his elderly father or a brother??? left behind who was too young in 1831?
We then can assume this William is on a homestead very close by......but there was no William as head of household in 1831: meaning he was too young to lead his own family then.
So again: would he be a younger brother of Thomas? he clearly wasnt a father....
It seems clear: your William Sr, Thomas and Robert are all related very closely.
To be born in 1809, my Thomas must have had a father born no earlier than 1790 probably.
And here is my gap: Who would that be?
Going back earlier: we get in 1766 on the Flax Growers list Thomas Crawford also of Ballycrum........so this at least must be the Grandfather or Great Grandfather of some of them.....no doubt born around 1745.......
My Thomas named his first son Robert as well: a further clue to a relationship.
It seems we need some Aghanloo information for about 1750 to 1800 to figure out who these men were and how they were related to each other.
Its a tiny area with a tiny plot of land to live on: the information must exist.