Esther Andrews Bishop was a sister of my ancester Neus Andrews. She's listed as Esther Bishop in the 1853 Census in Quebec living with family. Though it mistakenly says they were all born in Ireland, it would appear from this that she did not remarry.
John Bishop had at least four brothers that I know of, but I've only looked at John and Napthali. I believe the othes were Elijah, Samuel, and Timothy.
What record does your Cynthia Bishop first show up in?
Who/where did she marry?
Assuming she married, what were the names of her kids and where were they born?
With enough detail, perhaps she can be found.