The prohibition that results from breastfeeding is related to the issue of the male
وَحَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ الْعَنْبَرِيُّ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنِ الْحَكَمِ، عَنْ عِرَاكِ، بْنِ مَالِكٍ عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، قَالَتِ اسْتَأْذَنَ عَلَىَّ أَفْلَحُ بْنُ قُعَيْسٍ فَأَبَيْتُ أَنْ آذَنَ، لَهُ فَأَرْسَلَ إِنِّي عَمُّكِ أَرْضَعَتْكِ امْرَأَةُ أَخِي . فَأَبَيْتُ أَنْ آذَنَ لَهُ فَجَاءَ رَسُولُ اللَّهِ صلى الله عليه وسلم فَذَكَرْتُ ذَلِكَ لَهُ فَقَالَ " لِيَدْخُلْ عَلَيْكِ فَإِنَّهُ عَمُّكِ " .
'A'isha (Allah be pleased with her) reported: Aflah b. Qu'ais sought permission from me (to enter the house), but I refused to grant him the permission, and he sent me (the message saying): I am your uncle (in the sense) that the wife of my brother has suckled you, (but still) I refused to grant him permission. There came the Messenger of Allah (ﷺ) and I made a mention of it to him, and he said: He can enter (your house), for he is your uncle.