Since, 1880 Perry Co. Census shows Mary as mother of Stephen and Sarah, I have concluded that she is definately his mother. Unless I can connect Joshua to another family definately, I cannot with certainty state he is the father of Stephen.
It is simply more plausible for me to assume this is the case because all of these women were named Tadlock. If Mary was his daughter, her name should have been something else since she has children. 1850 census also lists a Susan Berry living in the household. I have wondered how she connects. It could be that Mary was a Berry also. This would still mean that the other women in the household were her in-laws.
Just another Mystery of the elusive Tadlocks!
Do you think Joshua is the father of your Albert J.?