I attempted to reply to the support post of the same name, but it was closed. I am experiencing this issue as well. The dropdowns for mother, father, and spouse are empty, even though there are other posts in the same category
The posts for my mother, father, and spouse exist in the web site. The WP Family Tree plugin is the only one activated. The site is a clean install of WP 3.6.1. I am using twentythirteen as the theme. The category is "family" as is the category selected in the WP Family Tree settings.