Well, after WWII, the Netherlands wanted to grab some German lands in a one-sided exchange. The major allies weren't keen on splitting up Germany so the Dutch settled for financial compensation of its war damages.
A stronger, bigger Netherlands (actually known as the low countries, not the low country

) might well get away with that demand. After all, whose going to stop them and they did suffer a lot in the allied invasion of Dutch Normandy

.
Lets assume they get the areas adjacent to Friesland like Sleswig-Holstein instead of the valuable Ruhr areas which are considered vital to Germany's future.
Denmark, which proved less than a speed bump to German aggression in 1940, realizes it cannot survive without an ally and turns to the Dutch, a country closely linked to its own culture and way of life as a fishing and trading nation.
In time, the alliance is cemented with royal marriages and a union.
Voila, low countries from Normandy to Denmark...
