I am in embedded, but doing more and more Linux C++ programming for my personal projects. I hope, I can transfer from embedded to “normal” software engineering in foreseeable future.
I know people who live fine with two kids on one phd salary (60k / year) or so. 120k CHF is definately enough to support a family. On 100k CHF you get already >7k CHF net, an apartment costs 2k - 2.5k if it is not in the city center and health insurance is 500 chf and food maybe 1k CHF more, so you can save 3k CHF every month. I run a tech recruitment firm in Zurich (coderfit.com), DM or email at iwan@coderfit.com if you want to know more.
Young kids are expensive in Switzerland if both parents work. But assuming one parent stays at home, 120k is enough to live a comfortable life.
Then if you're in embedded as per your profile, there are just so many more opportunities in the South of Germany, I'm not sure it makes sense.