I was wondering seeing as most of the prevalent languages are French and German, and during the time of the early Holy Roman Empire, they were subjects to the Emperor.
Here I am again to post my old posts again, reminding myself that I probably should ask the mods to add a Belgium section in the FAQ turns out I can do it myself:
It doesn't cover Luxembourg, though. I'm not too familiar with their history, but it seems like the fact that everyone wanted Luxembourg but didn't want anyone to have it allowed it to stay independent. It was part of the Habsburg Netherlands, but wasn't fully incorporated into the Kingdom of the Netherlands in 1815. During the Belgian revolution and in the following nine years, the Luxembourgians joined with the Belgian rebels - but during the Treaty of London, a deal was struck which would give Belgium the francophone area of Luxembourg and the rest would remain independent - but in a personal union with Willem I of the Netherlands. During this time, there was also a heavy Prussian influence in the heavily fortified duchy - mainly aimed at the French. Eventually, the grand duchy would remain independent because the Prussians didn't want the Dutch king to sell it to the French and the French didn't want it to go to anyone else either. With the second Treaty of London, it was just decided that it'd remain independent. That's just a basic overview though. It's a little outside my area of expertise.
The majority language in the Benelux is Dutch, not French or German.
Luxembourg has its own (Germanic) language, Luxembourgish. A common language always plays a major role in the development of a national identity. The Germanic roots of the language were brought up at various points in the 19th and 20th century in support of various agendas.
In addition, the capital city was a major fort until the (Prussian) fortifications were destroyed after the second Treaty of London in 1867 (note that there are several "Treaties of London" throughout history, but the ones in 1839 and 1867 have particular importance for Luxembourg). This strategic importance is one of the reasons why the Duchy, and later Grand-Duchy (after 1839), changed hands so many times in its history, and why so many claimants expressed interest when the future of the Duchy was at stake in 1815, 1839 and 1867. This eventually led to its being declared neutral. That last point probably had much to do with its eventual survival.
Luxembourg was given to William 1st of Netherlands at Vienna in 1815, in personal union. At the same time, it was part of the German confederation. A large part of the population joined the Belgian revolution in 1830, which led to a substantial part of the territory joining Belgium (the current Province de Luxembourg in Wallonia) at the Treaty of London 1839 (where independent Belgium was recognized). Some sources (including Wikipedia) give 1839 as the year of Luxembourgish independence, but this is not accepted by historians from Luxembourg. This point is referred to as the "Myth of 1839 Independence" in Luxembourg historiography.
Except for World War II, when Luxembourg was occupied, the defining test for the survival of Luxembourg was the "Crisis of Luxembourg", which was caused by William III of the Netherlands wanting to sell the land to Napoleon III. This was opposed by Bismarck, who used popular opposition to a "Germanic" land and people joining the France. The situation was resolved by second treaty of London, in 1867, which called off the sale, declared Luxembourg neutral, and required the Prussians to leave after disabling the fortifications at the capital city. The 1868 constitution survives to this day.
Actually the dominant language is Dutch, not french or german. About 23 of the 28 million people speak dutch.
Belgians might disagree though, one of their languages is Flemish but anyone from the Netherlands can understand it completely.