I've never thought of that. Why do you think so?

I have many reasons. He has same haicolour as Prussia has and same eyecolor than Austria have and I have seen a Cosplay video which name is Family day outside and in that is Prussia, Austria and Kugelmugel spending time outside as a family. I even found more pictures in DA where they are a family. In that vidoe Austria even calls Kugelmugel he so Kugelmugel is a boy not a girl even though he has long hair.

Hmm... but is there any historical reason for you to think that?

I don't think that they have history together. I just like this couple and Kugelmugel too. In other words I like PruAus and Kugelmugel. I don't exactly understand your question really well I am sorry. I don't understand everything in English because my mother tongue is Finnish.

i agree Kugelmugel is austrian and has the same hair color as Prussia and the same eye color as Austria, i like to think they are family :)