From Sahih Bukhari (Hadith 2647):
Narrated Aisha:Once the Prophet (ﷺ) came to me while a man was in my house. He said, "O `Aisha! Who is this (man)?" I replied, "My foster brothers" He said, "O `Aisha! Be sure about your foster brothers, as fostership is only valid if it takes place in the suckling period (before two years of age)
Reference: Bukhari 2647