NC for this.
Next door have two very loud children. They've been very loud for a couple of years and there was a lot of night waking that would result in hours of crying. They've done a lot of renovations and taken out a lot of their soundproofing so we can hear all of it. I didn't say anything to them as the kids were still so small.
There is also a lot of other household noise from them that we hear a LOT of. I occasionally book weekend breaks in remote places purely to escape their noise but it's hard to do that nowadays, and it's costly!
Their children are now approx 4 and 3 and share the room that backs on to ours. They shout at each other in the night, and start having screaming matches. I get woken up every day by them screaming, hours before I am woken by my own family. The youngest screams basically all day.
We have actually looked at moving purely because of noise from their children but can't afford it.
Should we say something? DH is equally annoyed by it. We WFH sometimes and you can hear them all day. It is mainly the night time that is an issue, though. The other day they were awake at 4, and subsequently , so was I. It isn't a one off. Last night the children were awake at 4.30am and arguing over something, that escalated in to shouting and screaming. It went on for a long time. I nearly started banging the wall in a sleep rage but didn't.