A couple ideas.....
FAN club ... Is anyone listed as witnesses on court documents (land records, Wills/probate), church records (baptism, marriage etc), newspaper records, neighbour in census records. Have you traced Christina as well? There’s a very interesting webinar on Legacy Webinar called “ The Five-story Fall: Correlating Indirect and Direct Evidence...” That provides an example of using the FAN club and unusual sources to extend research. (Legacy often provides some of their webinars for free)
DNA evidence. I’m still leaning more and more about how to interpret DNA evidence however in this case X DNA and YDNA lines maybe helpful for you. There’s a lot of very helpful webinars on Legacy that help with sorting out and interrupting the DNA evidence. I do think, however that DNA has to be combined with solid traditional genealogical research. DNA evidence may provide new clues for where to search further