My nephew is similar in regards to not being able to socialize properly with kids his own age. He's a great kid, but has a learning disorder and I think a slight ortism, not sure on the ortistic part, but the learning disorder is there.
He has just turned 18 and still can't read of write properly, which hampers his speaking in real life. He is pretty much ok and up to par with everything else though, so he's not too badly off.
I don't think it's too much of a learning disorder thing that is his problem, but maybe a confidence problem which has stemmed from the learning disorder, or something, not sure.
Either way, I don't thin you should be so hard on your nephew at first glance, maybe there is something wrong with him. He's only 8 years old, give the kid a break.