My two little ones age 2 and 3 keep getting hurt when DSC ages 8 and 9 are playing with them. They are too rough and have no concept of responsible play, choosing to play fight with (and around) them as though they were the same age.
This is particularly the case with eldest DSS (9) who picks them up and spins them around, plonking them down onto the sofa or throwing them down onto it.
After a particularly scary incident earlier in the year where DD (then age around 16 months) was dropped onto her head by eldest DSS onto the floor from his standing height as part of a "game" I imposed a blanket rule that they were not to pick them up again. I posted about this on here at the time.
They conveniently forget this despite constant firm reminders from me and I ended up having a row with OH about It after a further two incidents yesterday (and one last week where DD was whipped with a toy stethoscope which left a bruise because DSS was wafting it around near her)
DS was hurt yet again yesterday by eldest DSC body slamming him into the sofa yesterday 'playing' which resulted in him thumping his head into the hard frame on the back of the. DS was just sat on the sofa with his tablet minding his own business. This resulted in a 30 minute long meltdown where he was inconsolable and couldn't compose himself. He was in pain and his way of dealing with that was sadly to bang his own head repeatedly on the floor whilst screaming (he's autistic)
DD also got whacked square in the face by their football when we were at the park because they thought it was a good idea to blast the ball about where small children were playing, in the direction of said children.
My OH meekly addresses such things by asking them to apologise and be more careful because, in his mind, they are accidents and accidents happen.
If there is a particularly bad incident (the stethoscope is a recent example) OH will get 'no nonsense' about safety for all of 5 minutes but no real consequences are imposed, on this occasion youngest DSS just shouted at him then sulked. He came out of his mood after 10 minutes, made up with OH and all was forgotten.
When I was rowing about it with him today he said they don't mean to hurt them and it's just kids being kids for the most part although he can understand why I'm angry and he doesn't like seeing the smaller DC hurt either.
He said he doesn't know what the answer is short of telling them they can't play full stop and have to just remain seated (he was being sarcastic obviously) as he's told them so many times already and if they don't listen or retain what he's saying then he's at a loss because being boisterous and rambunctious is essentially who they are and the only alternative is to have them sat down playing on screens 
Im expecting a baby next month and to be honest I'm concerned about baby being hurt aswell. It hasn't always been this way they have gotten much 'worse' with age.
So tell me, is all of this is par for the course? Do you think it's to be expected that younger siblings will end up hurt by older siblings?
I'm at the stage now where I don't feel comfortable leaving them unsupervised and that isn't ideal because like every other parent, I can't keep my eyes on them for every second they're here, much less with a new baby.
I think I'm prepared to end my relationship over this, accidents or not.
AIBU?