When a woman breastfeeds an infant within the first two years, a maḥram relationship of "milk kinship" is established, so that the child may never marry that wet-nurse (his milk-mother) or those related through her by the same rule. Allah lists among the prohibited women "your mothers who nursed you and your sisters through nursing" (Quran 4:23), and the Prophet ﷺ said that what is made unlawful through birth is made unlawful through breastfeeding. There is a well-known difference of opinion over the number of feedings required to establish it — many scholars hold that five separate satisfying feedings are needed, based on the ḥadīth of ʿĀʾishah.
Evidence — the daleel
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.