When the house is tense, talk to your little sibling about normal stuff. Normal is its own kind of comfort.

Young kids read atmosphere long before they understand what caused it, and in a quiet house they often land on the worst explanation. Ordinary conversation tells them the world has not ended and that somebody still wants to hear about their day. You are not covering anything up by doing that. You are giving them somewhere steady to stand while the adults sort things out.

Ask about their game, their show, the thing they built, and stay for the whole answer. Keep one small routine going at the same time each day. You do not have to explain anything you do not know yourself.