The Messenger of Allah ﷺ said, "What is forbidden through breastfeeding is the same as what is forbidden through lineage, whether a maternal uncle, a paternal uncle, or a nephew."
حدثنا حسن قال حدثنا شيبان عن يحيى قال أخبرني محمد بن عبد الرحمن بن ثوبان أن
قال رسول الله ﷺ يحرم من الرضاع ما يحرم من النسب من خال أو عم أو ابن أخ
No references are available.
Its isnad is sahih, and Muhammad bin Abdul-Rahman bin Thawban is one of the trustworthy Successors, and his hadith is found in the collections of all six, and the hadith has already appeared at 24052.