Some of my ancestors were still in Germany at that time. I honestly don't know if any of them served in the war. I should try to find out.

Well, if they were male and of military age, it is possible. It was mainly a war between Prussia and France, but the other german states, like Hanover, Bavaria, Würtemberg and Hesse were also quickly siding with Prussia and sending troops. That was Bismarcks masterpiece, those alliances and the victory together, where what lead to the unification of Germany under prussian leadership.