Is it permissible for a stepfather to see his wife's daughters and shake their hands?

If a man marries a woman and consummates the marriage with her, all her daughters and granddaughters, whether by blood relation or fosterage, become forbidden to him. However, if he divorces her before consummation or if she dies, her daughters do not become forbidden to him. This ruling is based on the noble verse: "And your stepdaughters who are under your guardianship, from your women with whom you have consummated marriage. But if you have not consummated marriage with them, then there is no sin upon you." Accordingly, if your mother's husband has consummated marriage with her, then you and your daughters become mahram to him, and he is permitted with you what is permitted with mahram relatives, such as shaking hands and being in seclusion, provided that there is no fear of temptation.