Thanks for the additional information to help clarify the family you seek.
You state Robert (b. 1727 d. 1774) left money to his brother Alexander in his will probated in an unstated county. I assume that the Alexander you state married Pheobe Ramsburg in Aug 1775 is the brother mentioned in the will. But then you stated Alec married Maria in 1834 (there is a marriage record in DC for an Alexander Bever marrying a Maria Arrington on 1 Oct 1834) and after her death in the 1860's remarried Pheobe Ramsburg.
But if Alexander originally married Pheobe in 1775, and he was the brother of someone who was born in 1727, wouldn't Alexander have been in his 40's or so at the time of that marriage. How could he have then married Pheobe in 1775, married Maria in 1834 and remarried Pheobe in the 1860's? He and Pheobe would have been over 100 years old in the 1860's. Where did the remarriage of Pheobe and Alexander occur? Is there a marriage record for this?