I realize it has been a long time since this post, and likely you have found the information you seek, but thought I'd post this in the event you have not or it is helpful for someone...
I am NOT related to this line and therefore I do not have any additional information to add beside what I post here.
Thomas Speller, Martin County, TN will probated 1812 https://familysearch.org/pal:/MM9.3.1/TH-1-19459-54557-50?cc=1867501&wc=10922578
1) names heirs by last name of Sherrod (maybe sister's family?? just a guess) 2) names "my natural son" Thomas Monk
Thomas Monk, Martin County, TN will probated 1818 https://familysearch.org/pal:/MM9.3.1/TH-1-19459-54810-60?cc=1867501&wc=10922578
1) names his son Theophilus Hansel son of Polley Hansel 2) names his son Thomas Hagans, son of Susanah Hagans 3) names five children with MONK as last name: Nancy, Sally, Mariah, Joseph and Marthy 4) friend William Clark exec.
Out of curiousity, I would like to know why they have so many children with different names (I would think if they wouldn't say my natural child if it was their step child), but for those looking for ancestry, perhaps this information could help.