This quote is from The Four Loves by C.S. Lewis. My friend Jan sent it to Jody and I as it describes what happens in close friendships between 3 or more people. I love this quote and I hope it will augment your idea of friendship. I chose this book to illustrate this quote because the 3 friends Lewis speaks of are pictured on the cover.
Lamb says somewhere that if, of three friends (A, B, and C), A should die, then B loses not only A but “A’s part in C,” while C loses not only A but “A’s part in B.” In each of my friends there is something that only some other friend can fully bring out. By myself I am not large enough to call the whole man into activity; I want other lights than my own to show all his facets. Now that Charles is dead, I shall never again see Ronald’s reaction to a specifically Caroline joke. Far from having more of Ronald, having him “to myself” now that Charles is away, I have less of Ronald. Hence true Friendship is the least jealous of loves. Two friends delight to be joined by a third, and three by a fourth, if only the newcomer is qualified to become a real friend. They can then say, as the blessed souls say in Dante, “Here comes one who will augment our loves.” For in this love “to divide is not to take away.” Of course the scarcity of kindred souls – not to mention practical considerations about the size of rooms and the audibility of voices – set limits to the enlargement of the circle; but within those limits we possess each friend not less but more as the number of those with whom we share him increases. In this, Friendship exhibits a glorious “nearness by resemblance” to Heaven itself where the very multitude of the blessed (which no man can number) increases the fruition which each has of God. For every soul, seeing Him in her own way, doubtless communicates that unique vision to all the rest. That, says an old author, is why the Seraphim in Isaiah’s vision are crying “Holy, Holy, Holy” to one another (Isaiah VI, 3) The more we thus share the Heavenly Bread between us, the more we shall all have.”