Ugo Perego et al. determine through genetic testing that neither Oliver N. Buell or Mosiah L. Hancock are biological children of Joseph's.
Ugo A. Perego, Jayne E. Ekins, and Scott R. Woodward, "Resolving the Paternities of Oliver N. Buell and Mosiah L. Hancock through DNA," The John Whitmer Historical Association Journal 28 (2008): 128-136
[Perego et al. build on previous work reconstructing Joseph Smith's Y chromosome to determine that neither Oliver N. Buell or Mosiah L. Hancock are biological children of Joseph Smith.]