How Do They Connect?

A number of researchers have accepted the theory proposed that Peter was the son of a Jacob Rush and that Peter was twice married. His first marriage to Mary Cowell produced Isaac and Bethuel. His second marriage to Elizabeth Stull produced Charles, Paul, Phoebe and others. The Peter Rush who married Elizabeth Stull and fathered Phoebe, Paul, Charles, etc., is most likely the Peter in Monroe County in 1820. He could not be the father of Isaac as Isaac was born in 1785 and this Peter was born between 1775-1794. Peter Rush who married Mary Cowel is not his father either as this family has been documented and moved to Cuyahoga County, Ohio. 
Grace Suter Schafer, who was an early researcher of the  Isaac Rush family, said he had brothers named Jacob and Peter. She also reported the family said the Rushes came from Lancaster and Bedford County, Pennsylvania. My great-aunt Nola Jones, daughter of Mary Rush Jones, said the family came from Mt. Alpine in Pennsylvania. This location has yet to be located.

The oldest Rush in census records is Jacob Rush (b 1740-1750) and wife Prudance (as recorded in Monroe County land deed).
Their proven children are: 
    1. Mary b 1784 w/o Alexander Massie
    2. Samuel
    3. Margaret Culbertson born 1774 in Bedford County, PA.
While lacking documentation, all evidence supports the inclusion of these two as children of Jacob:

    4. Jeremiah b 1770-1780.
    5. Bethuel 1791-1852

These men were considered possible children, but it appears they may be nephews rather than sons:

    6. Peter b 1775-80
    7.  Isaac b 1785 
    8.  Richard b 1794-1800

The last Monroe County Rush is Elias. He was born in 1796, but is probably not a son of Jacob. 

It is difficult to identify Jacob Rush with a family in Pennsylvania, but he appears to be one of the Jacob Rushes of Bedford County, Pennsylvania. This leads to the obvious question. If Isaac was a son of Jacob of Bedford, how does Joshua Brown of Lancaster County fit into this? Why and how was Isaac and his children connected to Joshua? This confuses the migration pattern that the other PA Rushes followed to Bedford.
There is a Rush family in Northampton County, Pennsylvania, who have ties to Lancaster County. This family also has a Jacob and Peter Rush in it and the family is connected to the New Jersey branch that went to Somerset/Fulton. Could this be the missing link?
Could there be a clue in the Covalt family? Bethuel Covalt 1746 NJ - 1822 Tonoloway, Bedford, PA had children: Bethuel, Jacob, Isaac, Rachel, Martha (Jacob Hill), Sarah (Mathias Cowll). The names Bethuel, Jacob, Isaac and Cowll/Cowell stand out as being familiar to Isaac's story. Some of them went to Indiana, which is where Jacob Rush died about 1832. There are Jacob and Peter Rushes in the 1790 census in the neighborhood of Bethuel Covalt. What, if any, is the connection?
This is all theory! I would appreciate any documentation that proves or disproves any of the above information.
Updated 10/10/2013