Well, this one is very interesting being an elder child of parents can help you a lot. According to a study conducted by the team of Leipzig University in Germany, each child after the first child is slightly less bright as they have to share their parents.
The study suggested that first child gets an undivided attention of parents and that means they learn more in comparison to the younger ones.
However, this doesn’t mean that the first child remains dominating also. They have six in ten chances to have high I.Q still their younger siblings have a strong chance to become smarter.