Four of my grandkids and their mother live with me. It's all good. Age 4 and 5, 14 and 15. But to your point about boundaries, I have established what I call the Great Wall of Grandad. It's my virtual boundary that implies leaving me alone at all costs. My granddad's cave requires an invitation to come in if you are younger than 18. I have noise-reducing headphones and turned half my master bathroom into a coffee and whiskey bar. I'm geared up to spend hours in my room as needed.