From Sahih Bukhari (Hadith 2644):
Narrated Aisha:Aflah asked the permission to visit me but I did not allow him. He said, "Do you veil yourself before me although I am your uncle?" `Aisha said, "How is that?" Aflah replied, "You were suckled by my brother's wife with my brother's milk." I asked Allah's Messenger (ﷺ) about it, and he said, "Aflah is right, so permit him to visit you
Reference: Bukhari 2644