You may already have the answer to your question -- but yes these families are all connected.The families you list here - Samuel McConathy/McConatha and his children can be found on the 1850 Census for Alabama in Talladega County.Their name is listed as McConatha - which is probably due to the person filling out the census and spelling phonetically.
It also lists Samuel's wife's name as Nancy in 1850, but it does have her birthplace as Virginia.Their son James is 17 (he is a twin of Elizabeth). Marshal is only 3 years old. The 1850 census images can be found on genealogylibrary.com.
Samuel's father Joseph and mother, Isabella (Wilson) McConatha are also listed in Talladega County 1850.Also his brother Benjamin - who's name is spelled McConathy-- is in Talladega.Let me know if you have any other questions that I might be able to answer.