Those people that are self-centered, egotistical, selfish, greedy, and all about their own self, often don't develop very many close relationships, even if they are powerful and have a certain amount of charisma, because human relationships in order to be viable and healthy, necessitate a certain degree of reciprocity. This so indicates the true importance of a good rapport with others, and that good people understand the relationship value of understanding others.
In point of fact, the things and events that make up a given person, along with the motivations and disinterests that a particular individual has, varies considerably from person to person, and while it is true that those from the same family often have similar traits, so too, they also have differences, of which, some of those differences can be quite significant. This means, that while it is truly beneficial to know one own self, and quite frankly it is an obligation to do so, not all things that one knows about their own self, is particularly relevant to someone else's situation and what motivates them.
This means, that in order to really understand someone else, that most people need to put away their preconceived notions, and instead make it their point to actually try consciously to learn what they can about someone else. In addition, communication involves much more than verbal interplay, and should also ideally encompass eye contact, body language, and nuances, and from there to then take the entire process and try to assimilate such in a coherent way, and even then, it still might not even be fundamentally correct.
This signifies that even in those relationships of long standing, that rather than believing that quite obviously each person knows each other intimately, one should instead apply a healthy dose of humility and humbleness. For instance, asking questions about whether or not you understand something about another person, and then coming to an agreement about that understanding is of vital importance. So too, addressing questions about the relationship in which items such as in knowing the others' meaningful goals, as well as what is important to them, and then making it clear that you are there to be of help and of aid to them, especially when they are in most need of such, is the very stuff that makes for a very good relationship.
Far too often, people talk pass each other, in which neither party is really actively listening to the other, because basically they are eager to say what they want to say, believing in its overriding importance. However, these communication errors can be fairly readily rectified, by having the other person, sum up what has been said by that person that has been talking and not to continue the discussion until each party is assured that they have been successfully listened to.
Finally, there usually are plenty of people that will say that they love you, or that they respect you, but if they really don't understand you or know you on the level of whom and what you really are, than such love and respect, is at best, shallow. If, on the other hand, one makes the effort to know the other person, especially the things that are of the most importance to them, and makes sure to touch base and connect with them on a consistent basis, then that is caring, emphatic, and the very essence of agape love.