According to this Memory Alpha article on Richard Arnold, he is currently 54 years old.
If this is correct (and I see no reason why it would not be), Mr. Arnold would have been 18 years old when supposedly first met Mr. Roddenberry in 1972.
If this is correct (and I see no reason why it would not be), Mr. Arnold would have been 18 years old when supposedly first met Mr. Roddenberry in 1972.