Why are older brothers so damn over-protective?

It` s like your sitting in a car with them and their dropping you off and if another guy just looked and he was like ` what's that prick looking at?` or if your with them and some just guy makes convo with you they be like ` come on, lets go`

I`'e seen this happen with so many older brothers. they are just so over protective. It` s like chill out!
Why are older brothers so damn over-protective?
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