Need help trying to find Thomas and John Dempsey.

Hello,

I have come to a complete brickwall when trying to locate my Great-Great Grandmother's two brothers. Thomas Dempsey born 1864 and John Dempsey born 1868, they were born in Tyrrell County North Carolina. To William Dempsey and Angelico Bryant, they are listed on the 1870 Census with their parents and 2 sisters. But after that I cannot locate them, Angelico died sometime after the birth of her last child my Great-Great Grandmother Affie Dempsey. William remarried Angelico's younger sister also named Affie, but he was deceased before the 1880 Census was taken. I actually don't knew where Affie born about 1870 was during the 1880 Census along with her 2 brothers. Affie was still in Tyrrell County at that time but with whom I don't know. She got married in Tyrrell County in 1888.