Commune?

We have had what-if discussions with my brother how cool it would be to live in a shared apartment, or as neighbours, and now that things turned how they did we started to talk about that again, this time we were thinking of the advantages of commune living.

My brother and his SO are planning to buy an apartment from Metropolitan area and it wouldn't be much trouble to buy a bigger one (4-5 bedrooms instead of 2-3) (and in most cases it even wouldn't make it much more expensive), sublet 2 rooms to Tiny and me and enjoy all the good sides of commune: there would always be someone to look after Tiny when I need to go somewhere (this would be lovely as I would love to study while I am at home) and when I am sick I didn't have to worry about Tiny's wellbeing.
We could share household duties, we could buy food in bulk, there would always be food even if someone was short of cash before payday and there would always be someone to talk to - and when one would want to be alone there would be one's room.

I know it would be annoying at times, I have lived in communes when I have studied, but the advantage in this would be that I know 2/3 well: my brother I have known since birth and his son last 13 years. And brother's SO seems to be a person of reason from what I have deduced from those couple of times we have met. She's shy though, but it is never a bad thing.

And I would rather pay few hundred euros to my brother as it would be cheaper to live with them than in a regular rented apartment. And no need for rent deposits which means saving anything from 0€ to ~2500€ (or rather not needing to ask deposit from social services due low income).
Also it would mean that Tiny would get his own room and I mine as at some point he needs his own space - and us both being such restless sleepers it would make us both sleep better.