What type of elder sibling were you?

I have seen two types of elder siblings in families around me depending on how they react to the division of love they face when younger ones arrive.

One type hates the fact that their love is divided and parents take care of younger ones more than them and spend more time in caring the newborn. They hate their younger sibling while growing up.

Another one also does not like more attention given to the younger one and tries to behave like small kid to get more attention from the parents. Even after maturing, elder one behaves more childish because she thinks that it is the childish nature which is resulting in more attention from the parents.

In one case, elder sibling develops hatred for younger one in the process and in another one, they deliberately act childish to gain more attention from the parents.

I am curious to know how parents deal with this situation?

Curious about design, numbers and behaviour.