If we read the biography of imam Malik, we find that many members of his family were known by their studies of al-Athar (hadith) and religion in general. Among them are his uncles and his grandfather Malik ibn abi 'Amir مالك بن أبي عامر and also his Brother an-Nadr النضر بن أنس (see for example in Arabic wikipedia), while his father Anas ibn Malik was not known for studying hadith. It is even said that when he started studying people referred to him as "Malik the brother of an-Nadr".
I'd therefore expect that the name of an-Nadr should appear somewhere in either hadith collections or at least in collections of hadith narrators (books on 'ilm ar-Rijal).
Was Malik's brother an-Nadr mentioned in the narrator chain of any hadith among the 9 most authentic hadith collections of sunni scholars (the two sahihs of al-Bukhari and Muslim, al-Muwatta', the sunan of abi Dawod, an-Nasa-i, ibn Majah and a-Darimi, the Jami' of at-Tirmidhi and Musnad Ahmad) or were was he mentioned (a quote would be much appreciated).