1850 U.S. Census lists "Francis Custer" as 31 years old.
"United States Census, 1850," FamilySearch, Francis Custer in household of Soloman Custer, Dublin, Wayne, Indiana, United States; citing family, NARA microfilm publication (Washington, D.C.: National Archives and Records Administration, n.d.), accessed January 10, 2022
[1850 U.S. Census lists "Francis Custer" as 31 years old.]
If Fanny was born in September (as one obituary claims), then her birthyear would be 1818. She would have been almost 32.