Searching for John Clark's (1740-1818) siblings

There is Lavina Clark who may have been born ca. 1750, she married Caleb Hill before Feb. 1773. Caleb is in the 1790 census for Bedford. I am looking for more information about them.

David Hays Account Book, Bedford, 1770-1775

I received photocopies of the daybook yesterday. I will be scanning the pages that list purchases and payments made by our Clark ancestors. There are a few names of Clarks unknown to us, and I hope to trace them out to see if one or more might be siblings of our elder John Clark. Many payments made to John Hays are in the form of trading wheat, wood, labor, butter, flaxseed, other farm products, and sometimes cash. Many purchases are documented as "Sundry", being too small to list individually. Specified purchases are: molasses, rum, sugar, cloth, handkercheifs, hats, tea, shoes, brandy, salt, other household items, and spelling books.