i always thought an uncle was considered a mehram and couldnt marry his neice but lets say a man married his cousin and then wanted to marry her niece which is actually his own niece too? then wouldnt that be unpermissible since the girl would marry her aunts husband which is her uncle? imagine being a young sister living in the same roof of your aunt and being married to your uncle? this is haraam right?
isint it only permissble if its your long-distance niece?