Is my brother autistic?

I have a 5yr old brother.
For many years, ppl have been telling us that there may be something wrong with him. We have been ignoring it because he is hyper-active and it drives a few ppl crazy. I know they say it out of anger.

But a few days ago, i noticed that when he runs, he holds his arm in a strange way...
He holds it bent out wards, and hishands bent behind.
I have only ever seen that with autistic/downsyndrome children.

I told my mother and she just wont except it.

Also, he plays with toys and runs all around the house making noises like, explosions. I feel this is very strange.
Am i right to suspect??? Tweet