I'm a feminist, I've well versed in how parenting, peer pressure and the wider society can reinforce cultural stereotypes and I am actively trying to overcome that. But I still find myself doing it by accident sometimes. If you're not aware of it, or don't see anything wrong with it, you are bound to be reinforcing those stereotypes massively.
I actually think this has got worse in recent years. The rise of consumerism has spread massively into the toy market. Toys are segregated by gender more than they have ever been I think. It's reinforced through silly little things too, like putting a toy in a boy's party bag and a piece of jewellery in a girl's.
I am very grateful to have had b/g twins. By being at the same stage of development the fact that they play with each other's toys and do the same activities has much more effect on redressing the balance than it would if there were an age gap.