I've always given siblings gifts when a new baby is born so they don't feel left out. But the siblings have always been at most 4 years old.
Neighbour has just had a baby. Her eldest is 10 and often plays out with my DD. I don't know the mum very well as we have limited communication due to language.
Do you still buy a much older child a gift? Or assume they're old enough not to be jealous and don't need occupying when a half sibling arrives?