Actually, that's not correct. John Holmes and Tamar (Byrd) had only one child, Mary Holmes (my ancestor). All of John's other children were by a previous wife or wives; if they had been Mary's, she would've been bearing Patrick Carr's children when she was in her late 50s, which is highly unlikely. If you read the wording of John's will (where everyone seems to get the idea from that Mary was the mother of all of John's children), he never says that the children are all Tamar's, just that Tamar is his widow. Mary is the ONLY Holmes child named in Tamar's will. Tamar's children by Patrick Carr were Thomas, Jonathan, Winifred "Winnie," and another child I'm forgetting right now. John Holmes and Tamar (Byrd?)'s daughter Mary Holmes married Joseph Scott.
To date, I've yet to find any documentation to support Tamar's maiden name being Byrd, and your message is the first time I've ever seen potential parents named for her (although, again, it's highly unlikely she was born in 1691 if she was bearing Patrick Carr's children in the mid 1740s). Where did you find that info?
Please email me directly at email@example.com if you'd like me to send you the documentation that proves that Tamar is NOT the mother of any of John Holmes' children but Mary.