After German reunification the states of East Germany and West Germany ceased to be. Was that two genocides?

The two sides of this conversation seem to be using different definitions of the word "state".

I won't argue which is more appropriate in this context, but I think that's where the crux of the disagreement is.

That was their voluntary decision supported by the population of both states.

A closer analogy would have been some proposals to dissolve the German state forever after WW2, and get its parts annexed by other states. But that didn't happen.

Not to mention that Nazi Germany was actually doing an actual genocide. But that wasn't sufficient to warrant the same fate for them as a nation.

>But that didn't happen.

The latter part definitely did. See Konigsberg (now Kaliningrad, a Russian exclave) and all the parts of Germany that were ceded to Poland.

And the expulsion of ethnic Germans living in non-German lands across Europe postwar was certainly a form of ethnic cleansing, even if you believe it was justified to remove the justification Germany had for prewar annexations like the Sudetenland.