Many thanks to Sandra who tracked Joseph Watterson through his marriage to Gladys Pelling and the birth of their daughter Margaret who married Dale Lee Tryon. Perhaps Margaret Tryon is still alive.
Anyway, I decided to find Henry James Watterson, his cousin. I did find him on the 1930 census, single, with Viola Moore living in the same household. Apparently, he married her in 1932 and I found them on the 1940 census, in Philadelphia, with daughter Viola E. Watterson, age 5. And surprise! His uncle Adam, age 62, widowed, is living with him.
So I went in search of Adam. I had to work backwards but Adam married Susan Leslie Mar 21, 1913 in Magherafelt, Ireland and they immediately emigrated to Halifax, Nova Scotia, Canada in Mar 1913, then Adam crossed the border from Hamilton, Canada (presuming Ontario) to Buffalo, NY on June 19, 1913 and they are in Philadelphia by 1914 when their daughter Anna died. They had daughter Margaret in 1915, Elizabeth 1916, and Evine 1919.
Then Susan died between the 1920 and 1930 censuses, and the girls cannot be found in 1930 although I found Adam in 1930 and in 1940. I don't have the date of death of Adam or his nephew Henry James or Susan. But I am pretty sure Margaret died Sept 22, 2011 unmarried, in Philadelphia. If someone could find her obit, it could be very interesting.
Thanks everyone for all your wonderful help.
I tried to post the 1920 census for Adam but the site won't let me even after I resized it. Sorry
Peggy