Michael, I may have info regarding your family. My grandfather and great grandparents were from San Prisco. Much of their family immigrated to New Haven in the early 1900's, they lived and worked in New Haven for many many years.
The name D'Addio sounds familiar to me, but when your Italian every name that ends in a vowel does! My aunt has done a lot of research on our family and I will be contacting her soon, she also lives in New Haven.
I don't think it's a coincidence considering what you mentioned about the size of San Prisco and it's natives moving to New Haven! F.Y.I We also have family in Palos Verdes and Redondo Beach CA, both of which I'm sure you are familiar.
My family and I live in new Haven now and our family has grown to be rather large. Many diiferent last names have been married into the family but there are still many with origins of Monaco, Onofrio and Fusco, if any of those ring a bell.Please contact me via email so we can discuss our possible family ties.