Younger siblings and toys...

I don't think this would concern me. I would be telling myself he's bright and therefore toys that are deemed age appropriate are not stimulating enough.

My DGD 5 has never bothered much with her toys and will only play with her bigger brothers lego and constructions toys, so now thats what I get her.

Eldest GD has lots of toys but would rather play on a Nintendo or on the computer. New toys, bought for birthday last month, have been discarded already. her sister is happy to take the toys off her hands. Youngest can play on ipad but as she can't read rapidly loses interest.

My concern about siblings and toys is that toys that are safe for a 4 year old might not be safe for a 9 month old - and it is very hard to keep the two lots apart.

I think we've all been through that conundrum, Mishap. Mine were 21 months apart. The first word no 2 learnt was 'mine' because that was what big brother said when he swiped his toys. All the GC have caused similar anxieties but none of the younger ones ever swallowed a small piece of Lego or a hat off a Playmobile person. The only one who ever did was DS1, who had a peg board, looked at me defiantly, popped one in his mouth and swallowed it. It was subsequently found in his nappy.

This doesn't affect my two grandsons yet as the baby is only 10 months old, but I suspect that it will. It is already obvious that he adores his big brother and is hugely impressed by everything he does, so toys will obviously be the next target!

We've noticed this with our grand-children. The younger two have jumped stages in toys simply because they want to play with what the older one has. There is no harm in it.
It's always happened. I know I grew up faster because my sister was 6 years older and at 16 was out at work and talked to me about things, talk me to plays and museums, gave me books to read , that I wouldn't otherwise have had access to at that age.

Younger siblings always want what their older siblings have. They learn by copying. Normal ape animal behaviour.