Sibling Issues

Anyone that is a younger sibling, as an adult do your older sibling(s) take what you say into consideration like adults should; or do they just ignore or discredit advice you might give just because you're the younger sibling?

I ask because ive noticed my brother doesnt actually listen to what i say and gives me an "uh huh" to just acknowledge I even spoke, but he takes what our parents or any other older family members say as gospel.

We are both in our early 20s mind you, i figured that since we were both grown adults that stuff i would say would actually be taken into consideration and not just ignored.