At least I now know what you mean now.
In my opinion, and considering his qualifications and profession, I don't think interview skills and outgoing personality are going to have a great bearing on being considered by most organisations.
In the most complimentary way, would you consider your brother to be bordering on the eccentric?
If so, then have a cross sectional look at most of our Professors and the great technical minds of our time (not saying that they are all in the same category). "Social outcasts" would be a light term for many!
Of course the shyness aspect is going to have a bearing on the so called "teamworker" requisites of certain oraganisations, but this requisite is not common to all.