What are the prohibitions established through affinity/marriage relations (Musahara)?

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There are four explicit prohibitions via affinity. First, mothers-in-law: any woman a man marries makes her mother forbidden to him, whether related by kinship or fosterage, near or far, immediately upon the contract ('Aqd). This is based on "and the mothers of your wives" (Quran 4:23), which applies generally, contrary to the view that prohibition requires consummation. Second, stepdaughters (Raba'ib): they are forbidden only upon consummation (Dukhul) of the marriage with their mothers, based on "and your stepdaughters who are in your laps [i.e., raised by you]" (Quran 4:23). General consensus holds that the prohibition applies if the mother was consummated, regardless of whether the stepdaughter was actually raised by the husband, though some permitted it if the stepdaughter was not in his immediate care. If the marriage to the mother is dissolved by divorce before consummation, the daughter is generally not forbidden, unless the mother dies before consummation, in which case there are differing views regarding whether the death substitutes for consummation. Consummation is defined as sexual intercourse; seclusion without intercourse does not render the stepdaughter forbidden according to the view relying on the explicit text of the Quran.