Francis McLernan had a sister, Mary, who married Augustine McCurdy. They had five children including Joe, who I met, Cissy who was probably actually Mary Margaret (I had an Aunt Mary who was always known as Cissy) and Alexander.
Your Grandfather wouldn't have known about James Alexander Born 1889 and died 1891 or Thomas born 1890 and died sometime before 1901.
So they were First Cousins of your Grandfather.
I take it your grandfather married Mary Bresland and produced four children, that I know of, two girls and two boys - I don't have their given names or any other details(Hint, Hint).
My grandfather, Patrick Kelly was adamant that these Augustine McCurdys were HIS cousins. He was never wrong on these matters but after MANY years I can't find the link. However he classified and regarded 2nd, 3rd and 4th cousins just as "cousins".
There is another McCurdy link in your lines. Francis McLernan, your great grandfather was named after his grandfather, also Francis, who would have been born about 1785. This Francis married Mary McCurdy who, although not yet proven, was very likely to have been a Rathlin McCurdy.
Hope this was a bit of help