What then are things that lead to relational depth and thereby maturity?
Time given freely, in seeking the good of others and finding out what that good is. "I didn't know" implies the potential for growth in maturity.
Knowledge of someone, who they are, what they need, what they can contribute and then facilitating that contribution.
Commitment, in that one is in the relationship through good and difficult times, embracing the changes that one needs to make in themselves in order to make relationship work.
Resources dedicated to depth of or deepening relationships, recognizing and embracing personal cost.
Sacrifice in the willingness and conviction to give one's life for another as Christ did for us (Phil 2:1-11).
Vision for others as an aspect of spiritual maturity for all believers independent of personal characteristics (Colossians 1:28-29).
Desire for relationship and depth in relationships too.
The word increased, implies movement toward an objective that has no point of achievement or arrival. We are constantly striving, seeking betterment, seeking improvement, seeking intimacy, and constantly striving.
How does change occur? It comes through awareness intentionally, unafraid of change and of being changed, knowing Biblical plans and God's plan moving toward a vision. Knowing where you currently are so you can move forward toward a Biblical understanding of relationship among all people. Being reflective about relationship is a critical aspect of change. Intentional shepherding and care of everyone, not just from the leadership, but the responsibility of all towards all.
Some of these aspects of maturity might seem a bit redundant, but it is like a multifaceted stone that you turn around and around looking at the same thing in different ways, sometimes perhaps feeling like it's the same thing but actually revealing different facets of the the stone.