Is my brother autistic?

[Alex]

I think he's just socially awkward but attached to your mom. I hate to break it to you, but most boys/men watch some form of porn.
As far as autism goes, you need to realize that autism is about not understanding situations and other peoples emotions. From what you have told me, I doubt it.
For example, if he was talking about cars to someone who clearly doesn't care, if he was autistic, he would continue to talk about cars whereas most people would realize and change the subject.