Allison is a male. First-born of W.K. Denson and his first wife, Nell. I don't think Mary is her name also, but I may be wrong on that. Perhaps her first name.
Thanks for the catch! From the geneaology I found on the web (which could easily be wrong), it had Nell Denson's actual name listed as "Mary Nell Denson", so I'll leave it that way for the time being, but I changed her display name to "Nell".
Thanks so much for your help! I was super confused with Allison Denson since the name looked like a girl, but was listed as a son, so I didn't know what to think.