I figured they would.
Maybe with a different German unification, a more powerful Austrian Empire arises, owning lands into Bavaria, and more of Southern Germany proper. Let's say that some Archduke analogue is assassinated in some Serbia analogue, and an alternate world war arises because of that.
WWII is similar to OTL, except around Austria rather than Germany. I mean Hitler was Austrian anyway, and is idea's were nowhere near new or original.
With a POD 100 years ago, it is hard to accurately predict what would happen. Some form of German unification is probably inevitable with a POD in the 19th century. Though the kind of unification is not. OTL unified Germany excluding just Austria is not certain. I consider it possible that Germany unifies in a EU kind of way. A bunch of still more or less independent countries, that cooperate in many ways. Or two Germanies: a southern Germany and a Northern Germany. Or various parts of Germany outside of Germany (like Austria OTL). Maybe Germany unifies, but Prussia and Austria remain outside it. Etc. All will have a major effect on what kind of wars happen in the 20th century.
The most important factor a unified Netherlands would have had on the unification process of Germany is Luxemburg. Luxemburg was part of the German confederation (in this case Dutch Limburg will not). The Netherlands would have wanted to integrate Luxemburg fully into the Netherlands (just like it di OTL with Limburg). If we assume equal rights for Walloons (the only way a united Netherlands will prevail), I am certain the Walloon Luxemburgers would want that and I don't think the others would have minded, they were relatively satisfied with the Dutch rule. The question is, would Germany or Prussia accept such a thing? When Denmark tried to do something similar with Schleswick, it did not. The problem is that attacking the Netherlands will certainly drive the Netherlands into the hands of the French (assuming France drops any claim to Belgium, which would be the smart thing in this case). The Netherlands was always friendly with Prussia, so it might not want to do it. It also might sour relations with other countries as the Netherlands had a pretty good relation with Russia and I expect the Anglo-Dutch relation will be pretty good. Anyway the risks of interfering in the Netherlands might simply be too big for Prussia to do anything.
In any case this leads to no Luxemburg crisis (the Netherlands or the Dutch king is not going to sell luxemburg), which means a better relationship with France, possibly avoiding the Franco-Prussian war and thus at least postponing the German Unification. My guess would be that Bavaria and Würtemberg (and possibly even Baden) stay out of Germany, possibly even forming a Southern German confederation, thus creating a very different political situation in central Europe, which will lead to a very different early 20th century. A major war (or two) is still very likely, but it will be very different than OTL.