Reliability & validity in measuring personality traits

Self reports from the person being assessed may lack validity because how a person perceives themselves is not necessarily how they are actually like in real life. For example, a person may believe that they are kind or generous, but refuse to donate to a charitable cause when the opportunity arises. Reports from close friends or relatives of the person being assessed are not always accurate either, as their reports may be skewed, depending on their relationship with the person being assessed. Someone who has a good relationship with the person might describe them in a more positive light, while those with a weak or bad relationship might describe them in a more negative light. In the case of the person being assessed by a trained observer, reliability and validity of the assessment can be questionable because of the time restraints. Though the observer is trained, it is difficult to judge a person's entire personality in the span of, for example, a couple hours, and would only be a small portion of the assessed's personality. 

I would argue for the superiority of the reports from close friends and relatives of the person being assessed, because they have known the person for the longest amount of time, and have seen, and been able to judge them in several different types of situations. Though their reports might be biased, they would still have the closest idea to the person's actual personality, and it would simply take reports from several different people to get a more accurate description.