From Wikipedia:
Muslims believe that Zuleikha, after many years of suffering and longing and eventually becoming a true believer, ends up marrying Prophet Joseph.
Does Islam teach that Joseph married Asenath? If so, does that mean he eventually married his mother-in-law? I cannot find this part of the story directly.
Genesis 41:45 JPS
One other reference:
Reflecting on these verses suggests that she had turned to Joseph's religion, monotheism. His imprisonment was a great turning point in her life. After this, the Quranic style neglects the story of the chief minister's wife completely. We do not know what happened to her after she gave her clear evidence. Yet still, there are legends about her. It has been said that after her husband died she married Joseph, and, behold she was a virgin. She confessed that her husband had been old and had never touched women. Other legends said that she lost her sight, weeping for Joseph. She abandoned her palace and wandered in the streets of the city.