Thanks so much for your reply!
Do you know if your great grandmother Mary Challenger had any siblings? I was told that my great-great grandfather John Henry Thomas Challenger had a sister named Mary A. Challenger. He was a widow when he married my great-great grandmother Susannah, and my aunt told me that he had three children with his first wife (whose name is unknown.) The children were named Mary, Barbara and Pine Challenger.
Do you know the names of any of the parents of your Mary Challenger and Samuel Barnes? I can't seem to find anything on either the Barnes or Challenger families in St. Kitts, except for Edgar Oscar Challenger, whom I'm assuming we're probably related to in some way or another.