My wife's maiden name is Mary Seabrook and a proven descendant of Captain Robert Seabrook (1652-1710). I have virtually all his descendants in my Family Tree Maker program, starting with "The Early Generations of the Seabrook Family" in the 1916 issues of the South Carolina Historical and Genealogical Magazine. I have 25 "Southern" Mary Seabrooks but none matching your 1812 birthdate in Pennsylvania. It is possible that a Seabrook went north in the War of 1812 and had a child there, but most of Robert Seabrook's descendants settled in Colleton County SC (Edisto & Seabrook & Johns Island)or in Savannah GA. You should be aware of the "Northern" Seabrooks of Samuel Seabrook, Arthur Seabrook, and "Spinach King" Charles Franklin Seabrook, and John Seabrook's articles in the New Yorker Magazine in 2001. There were many freedmen that took the name of their owners and may have gone north. I suggest you look for a Seabrook family in a Pennsylvania 1860 or 1870 Census.