Netherlands/Luxembourg is an uncommon pairing involving the characters Netherlands and Luxembourg. This pairing is also known as NedLux, depriving from the first three letters of their names. It is also called NethLux and Tulip Brothers.
Netherlands and Luxembourg are both brothers, with Luxembourg being the younger one. Not much is known about these two but it is confirmed that Luxembourg highly regards the Dutch.
This was proven by the fact that he is taking examples of Netherlands' actions to improvise his own needs or to upgrade his country for example on how Netherlands overcame poverty, on which he asked his sister Belgium about it. He also compliments on Netherlands' arts and gardens, saying about how nice they are.
He once attempted to mimic Netherlands' hairstyle but since his hair was soft, it turned out to look fluffy and tangled in one of his scrapped designs.
Even so, Netherlands said that he doesn't want Luxembourg to follow his actions. They get along very well and have talks about economics, on which Belgium "doesn't get much of what her brothers are talking about".
Some fanfictions involving this ship add Belgium as the 3rd wheel.