One wonders whether there are any who truly understand what it means to be a family. I myself sometimes have difficulty understanding the truest concept of family. So, when God tells us that his kingdom should be as a family of brothers and sisters, mothers and fathers, the concept eludes us. Families are too varied and too complex in their configurations to enable us to conceptualize the sense of unity that God expects and intends that we should create as disciples in his kingdom. We need to move beyond humanity, and look instead to other elements in nature that most clearly exemplify the concept of family.
Think of a forest, for example, that consists of one hundred trees. Some of the trees are full grown, others are young trees, and others are mere saplings. Between the trees are weeds of every kind. The trees are unmovable in their relationship to each other, unless they are cut down or destroyed. They never try to move to the front of another tree, nor do they ever try to undermine another tree by toppling it over. They share the nutrients from the soil, each getting as much as it needs in relationship to the other trees. They also offer shade if another tree cannot receive direct sunlight. When their leaves have served their purpose, they release them to the soil to be recycled for the benefit of all.
Trees "know" that they can be uprooted at any time. Thus, when they aspire to reach new heights, they know that they must send their roots deeper into the soil. Some of the sturdiest trees have roots that, in length and depth, surpass their height. Similarly, anyone who aspires to enter the kingdom of God should know that they too can be toppled and uprooted at any time, and their singular defense strategy should be deeper spiritual roots, a deeper and more abiding faith in God, and a relentless pursuit of righteousness. Then they can be guaranteed of God's protection.
Family in the kingdom of God is an unbreakable bond. You will never have an opportunity to change your mind about the need for the relationship, to get a divorce, or to move to a distant city. You always will be in relationship with each other, growing and changing as circumstances demand, and drawing closer to each other with every new challenge. That is God's concept of heaven on earth, and that will be the reality in his millennial kingdom.