I have 4 (soon to be 5) DC. I definitely do not leave my older ones to raise my little ones. None of my children have ever been expected or even asked to change a nappy or feed a younger sibling. They are expected to help out around the house with cleaning jobs but nothing strenuous or unfair. Ds14 is expected to load/unload dishwasher and Hoover once or twice a week (just the living room.) my DD9 has the job of bringing down washing and taking up clean washing and will have a go at hoovering every now and again. The little ones are just encouraged to help with things like picking toys up, taking cups and plates to the kitchen etc.. everyone helps out with a general tidy up after tea through the whole house, toys away, table cleared kind of thing, and they are all expected to keep their own bedroom tidy, put their clean clothes away and make their beds. All cooking, dusting, moping floors, ironing, washing is all done by me and DH.
We are about to move to a bigger house so everyone gets their own bedrooms (currently 2 little ones share) so everyone can have space and somewhere quiet to escape to if needed.
I am also really REALLY lucky that my DH is amazing, he works so hard and has a good job so we have a good standard of living without me needing to work for now, I did work until my youngest was born but one of us really needs to be home with them for a few years especially as one has special needs. DH will come home and get straight in with kids, cleaning, cooking... basically whatever needs to be done right then. I actually could not do it if it wasn't for him, especially with newborn/pregnancy stuff. Our house is more often than not loud and fairly chaotic but everyone is happy, we have quiet times of the day and busy times. We make sure everyone gets quiet time with us, I have all morning with my 1 yr old then all afternoon with the 4 year old while baby sleeps, then the 14 yr old will often pop down for a chat in the evenings when everyone else is asleep. 9 year old tends to spend more time with DH as they share a hobby that they love spending time on.
Sometimes it does feel a bit crazy but I had the same feelings when I just had one and it just means taking a step back for a second and working out what needs to happen to regain control. I worry that when I'm out people judge us but not for long, we're generally too busy to notice the tuts or glares.
I realise this comes across as a bit smug, I'm not trying to be, there are definitely times that I think fuck, what have I done. But in general I think we had the kids for the right reasons and I hope we're doing a great job raising them.