Well, this is going to be a confusing one.
Basically, my wife, first son, and myself are British citizens. We moved to Australia a few years ago (my visa is that I am a permanent resident in Australia, along with my wife and first son).
My second son was born a year ago here in Australia. He is an Australian citizen.
We are going to visit family in the UK in a few months and need to know what visas we will need, if any. Ignoring Brexit, of course (if they manage to get that passed before then, and who knows what form it will take).
Now, as I, my wife and first son are still British citizens, I imagine we don't need any visas. However, I think we'll need to apply for something for our second son.
Also, we're looking at visiting Europe whilst there. Again, as British citizens (while the UK is still part of the EU), I imagine that I, my wife and first son will be fine, but we may well need to apply for something for our second son.
Am I right in thinking this (and also that, as a family unit, we'll have to enter the UK via the "from outside the EU" queue at our destination airport), and if so what do we need to apply for?