How to encourage siblings to share with an age gap?

[Anythingforcake]

Evening 😁
I'm hoping to call on you all for some wise advice. I have a 5 year old and a 21 month old, they get along lovely but I've run into an issue with sharing and taking turns. The 5 year old knows to share and will take turns however the 21 month old isn't really at a point developmentally or linguistically that it's appropriate to expect her to share. Obviously the 5 year old then resists sharing and taking turns because it's hard to encourage the younger to do the same. Obviously we are encouraging her to and try to keep things equal but also we can't be too strict because she's too young to understand.

Does anyone have any good tips for reducing frustration all round? TIA!

Give the 5yo space, and places where they can play without being disturbed, and let them take toys to it when they need a break.

Otherwise it's easy to fall into the issue of "they don't understand, just let them have it" and at that age they constantly want what the older has.