One or two sucks do not render marriage prohibited

‘Ā'ishah (may Allah be pleased with her) reported that the Prophet (may Allah's peace and blessings be upon him) said that if a baby sucks once or twice from the breast of a woman other than his mother, this does not make him her milk-son, nor does he become a Mahram to her, because the conditions of the prohibition are not complete. In a breastfeeding that renders marriage forbidden, the suckled child is not permitted to marry the woman who breastfed him, nor any of her blood relatives or the blood relatives of her husband, who owns the milk [it is his semen which caused the pregnancy that stimulated her lactation]. This type of breastfeeding makes it permissible for a suckled child to be in isolation with those mentioned above, and to be their Mahram when traveling. One or two sucks do not prohibit marriage; five or more sucks are required, as the other Hadīth of ‘Ā'ishah says: ''...

so they were abrogated by five known sucks.'' [Muslim]