My 20mo amazes me every single day. She gets the hang of things so much quicker than her sister did at her age, and in many respects still does. I think the second sibling (especially if they’re the same sex) benefits greatly from the older one.
A good example is that we bought our 4yo a lovely wooden toy kitchen and all the accessories for her second birthday. It has been played with every single day since, and is still very much her favourite thing. The little one has been playing with it since she was able to cruise the furniture at nine months. A whole 15 months before we even had it in the world of 4yo.
The same has happened with 4yo’s scooter. She didn’t have it until she was almost three, yet her sister started playing with it before she could even walk. Last week she hopped on it and has been tentatively riding it here and there since.
This morning after the school run, she rode it all the way home. Granted it took about twenty mins to get back rather than just five, and she did fall off a couple of times, but she picked herself up instantly and got straight back on the horse as it were. It was really fab seeing the joy on her face!