It is very difficult in theology to avoid either:
1. Collapsing everything into a single static ONE.
2. Breaking-up everything into a multitude of distinct and autonomous MANYS.
The metaphor (or reality) of family relations is one way - probably the only easily-comprehensible and psychologically-effective way - of doing this.
In a family all are related - hence there is unity; but each family member is a recognized individual, one-of-a-kind (even among identical twins) - hence there is uniqueness.
(At a higher level, each family is linked with others in a 'clan' or extended-family - hence unity; yet each family is recognized as different. And so-on upward. )
Break the family, and this breaks down.
In modern secular society each person is either one of humankind - which is so large a unity that it has no felt unity in the absence of smaller, nested, hierarchical unities (not least since the borders between humans and animals are fuzzy, for secular modernity); and there is the individual, one of a kind person - but so individual (one is six billion) as to be incomprehensible.
To have a unity of seven billion and a uniqueness of one-in-six-billion are necessarily abstractions; and abstractions are psychologically unreal - so a person's unity with other and also their individuality become alike theoretical rather than experiential.
Alienation from the group, anomie of the individual... That's modernity; that is the lived reality for many, and the reality for all on the other side of the destruction of the family.
So the family is indispensable for society - and the truth of family relations also indispensable for theology; because only life as essentially familial can explain, in a way that is both comprehensible and real, how it is that the world is both one and many - that everything is both God and also itself.