Is it permissible to marry the sister of one's father's wife if the full sister of the married person was nursed by the father's wife?

The sister of the stepmother is not a mahram, and it is permissible to marry her, based on the general import of Allah's statement: "And lawful for you are [all others] beyond these." Furthermore, the fact that the questioner's sister was breastfed by his stepmother does not prohibit him from marrying the stepmother's sister.