Thanks to this board and members of the Washington County, NY board I was able to put some family clues together. I was sent information from the NY 1855 and 1865 census showing Miles Foley Sr. was dead by July 1855. These census also showed that there are more children of Miles and Margaret Foley than just Miles Jr and Marg Jr.
William Foley was born in Poultney, VT in 1849, Bridget was born in Poultney in 1851 and Patrick was born in NY in 1853.
Miles Sr signed an US allegiance oath in NY in Oct 1853 so we can assume he died in NY between 10/1853 and July 1855.
Now knowing that they lived in VT when they first came to this country I searched 1850 Poultney Census and found him listed as Milo Folrey. Included in the family was Margaret Sr's brother Patrick Cavenagh born in Ireland abt 1830.
The family didn't even know of the three new children as it was never in any old family histories.
If anyone finds any info on WIlliam, Bridget or Patrick Foley or Patrick Cavenagh (spelling could be different) let me know.
Thanks for you help in the past and the future!