I think it's part distance/ personality and part cultural difference.
You meet very rarely so barely know each other, you simply can't have much of a connection from such distance. I see my extended family with similar frequency and to be honest, I don't know them and seeing as I don't know them, asking them any such questions would be kind of hollow.
I'm from a country similar to Germany culture-wise. Honestly, when I first came to the UK, I found people quite intrusive. They'd be asking me how I was and how my work etc was going etc. Over time I realised that this was normal in the UK and people were just a bit 'nosy'/ making conversation was considered polite, compared to Northern Europe. People thought I was rude, as from my life experience so far, I considered asking personal questions inappropriate, so I didn't ask such questions back.
Especially if they are in East Germany, but generally Germany and similar countries, asking personal questions from someone you don't have regular close conversations with can be considered impolite and intrusive. I understand in a way you may consider them your family, but if you don't speak to them on personal topics on a weekly basis, they may think it odd to have this type of conversation.
It may sound cold but it's often better to stick to generic topics such as what is happening in the public domain/ news etc. Especially if you are in a group. 1-2-1 personal questions are more acceptable.
Again, this is my specific experience of living in Germany and Northern Europe, so your partner's family may be a bit different.