The Prophet of Allah ﷺ said, "A single suckling or two sucklings do not establish the prohibition of marriage."
حدثنا معتمر عن أيوب عن ابن أبي مليكة عن ابن الزبير
أن نبي الله ﷺ قال لا تحرم المصة والمصتان
Its isnad is sahih. Its narrators are well-known figures. It is found in Muslim 2/1074 no. 1451, and Tirmidhi 3/446 no. 1150, where he said, hasan sahih. Also Nasai 6/101 no. 1942, both in the chapter on breastfeeding, and Abu Dawud 2/224 no. 2063, and Ibn Majah 1/624 no. 1942, both in the chapter on marriage.