Big siblings have a big influence on shaping families.

Studies show that sibling behavior is influenced by how the older sibling acts.

Researchers from Brown University looked at how an older sibling who smokes or drinks affects the younger sibling.

They found that if an older brother or sister smokes, the younger sibling is 25 percent more likely to follow suit, and they are 36 percent more likely to drink alcohol if their older sibling does too.

Another study that looked at teen pregnancy found that if an older sister gets pregnant, the younger sister is five times more likely to also get pregnant at a young age. Of course, younger siblings can also copy good behavior exhibited by their older brother or sister.

And sometimes siblings turn out completely different from each other.

According to Laurie Kramer, a researcher from the University of Illinois: “There are many cases where younger siblings work very hard to carve out their own unique path and be different from their brothers and sisters, a process researchers refer to as ‘de-identification.’”

Many behaviors are also learned from parents, but as this research shows, older siblings have an effect on the younger ones.