Do not be sexually intimate with one’s sister who is his father’s wife’s daughter.
“The nakedness of your father’s wife’s daughter…. you shall not uncover “Vayikra 18:11
This means when she is one’s sister.
If she is the daughter of one’s father’s wife by another man she would be permitted to him to marry.
This only applies when she is his sister and is punishable twice, including above -127.
There is no separate death sentence by the Jewish courts over this, only spiritual severance applies.
If done unwittingly a sin offering is required.
This applies in all places at all times.