Is it permissible for Hamza to marry Suhayla, knowing that Hadda—Suhayla's mother—nursed Hamza once?

If a woman breastfeeds a child under two years of age, the child becomes her son. Scholars have differed on the number of breastfeedings that establish prohibitory kinship (mahramiyyah). The Hanafis, Malikis, and Hanbalis (in one narration) hold that prohibition is established by a single breastfeeding. However, the Shafi'is and Hanbalis (according to the most authoritative view in the madhhab) stipulate five breastfeedings for prohibition, and this is the relied-upon opinion for fatwa. Based on this, if a woman breastfeeds a child only once, prohibitory kinship is not established, and it is permissible for him to marry her daughter. Nevertheless, it is more cautious to refrain from such a marriage, out of consideration for the opinion of those who hold that prohibition is established by a single breastfeeding.