Genealogical databases sometimes want us to know more than we do and encourage us to conclude more than may be actually implied in the record. An estate settlement from the 1870s indicated that the deceased was survivied by the children of his sister--and then it goes to name her two sons and one daughter.
The sons have the same last name and the daughter is listed being married.
Nowhere in the records is it stated that the daughter is the full sister of the two sons. They easily could have been half siblings and the court would not have cared.
Be careful when doing data entry that you do not enter more than the record states.