I listened to the Confessing Baptist Podcast #42 aired on February 18, 2014, which featured Pastor Larry Vincent on Baptists and Two Kingdom Theology Part 1. I had never thought about this topic in terms of the biological family or the culture, so I thought it would be helpful to share the insight of Pastor Vincent. I am quoting extensively from the interview; therefore, I've made minor grammatical edits to the text below to help the reading flow (any emphasis is mine).
What is the doctrine of Two Kingdom Theology? As Paul taught in his epistles, our citizenship is in heaven. While we are in this temporary age in the nation in which we have been providentially placed, we have an obvious citizenship in an earthly nation, but nevertheless, we are pilgrims and sojourners here; and therefore, via faith in Jesus Christ our New Covenant King, we belong to a coming eternal kingdom or age. The truth of the Two Kingdom Theology is that we are in a common kingdom under the Noahic Covenant and in the spiritual kingdom under the New Covenant.The Covenant of Grace is promised in the Abrahamic Covenant, but it is not accomplished until the New Covenant. This takes the whole concept of the place of the biological family out of the equation which is foundational to the understanding of Two Kingdom Theology. The Covenant of Grace is accomplished and implemented in the New Covenant, which means the biological family is really out of the equation the way the paedobaptists view it. As [Reformed] Baptists we catechize our children; we do not undermine our responsibilities as parents for our children, but we see them outside of Christ, outside of the Covenant, because our children are people who need to be evangelized in the process of their upbringing...We are to be focused on our primary human relationship which is our church membership, an eternal human relationship in Christ...The Two Kingdom Theology frees us from the confusion of including the biological family in the spiritual kingdom, when it is obviously part of the common kingdom of this temporary age. Mothers and brothers are those who do the will of God, thus the character and shape of the New Covenant family is not the biological family, but we do pray that our children will become part of it and work toward that end.Quoting from Living in God's Two Kingdoms by David Vandrunen: Our responsibility in our nation, the common kingdom, is anchored in the Noahic Covenant, (Gen. 8:20-9:17). This is the scriptural foundation of our relationship with our nation that we find ourselves living in by God's providence. This Two Kingdom doctrine strongly affirms that God has made all things, that sins corrupts all aspects of life, that Christians should be active in human culture, that all lawful cultural vocations are honorable, that all people are accountable to God in every activity, and that every Christian should seek to live out the implications of their faith in daily vocations. A biblical Two Kingdom doctrine provides another compelling way to look at this whole issue of culture. God is not redeeming the cultural activities and institutions of this world, but is preserving them through the covenant He made with all living creatures through Noah. It is important not to make Christian ghettos, but it's also important that we not saddle ourselves with this impossible redemption of our culture or society. We take felt guilt upon ourselves, not biblical guilt. We are not responsible for the decay of our culture; if anything, we are a preserving agent. We do not want to presume upon our God, if He chooses to see the decay of our culture and raise up another, that's His business; our job is to be faithful. Therefore, Christians should be concerned with reforming their life to meet those things regarding sanctification, holiness, and the personal pursuit of Christ in the Scriptures. That's what we reform. Are we to be culturally active? At times, yes; and at times, no. The local church is not a resource for fixing the culture that we live in.What is the relation of Christian liberty and the Ten Commandments to Two Kingdom Theology? Two Kingdom Theology teaches us to focus on fulfilling the dictates of Christian law and ethics in both kingdoms. The confession [LBCF] fleshes out the law of God and distinguishes it from the commandments of men, while liberty stays in place; but liberty is not license. It is clear in the confession and Scriptures that we are taught to pursue holiness and to follow the dictates of Christian law and ethics in both kingdoms; therefore, we should properly fulfill them in both kingdom. As Americans, we tend to confuse the two. We have different responsibilities to our local church, which is our primary expression of our responsibility to the spiritual kingdom, than to the common kingdom. The local church is not a resource center for money and time and energy to fix the problems in this culture. We are to look at our church as a place of resource (money, time, & energy) to accomplish the reformation primarily in personal holiness that Christ has called us to, which God may or may not use in the changing of the culture around us.
"Wherefore gird up the loins of your mind, be sober, and hope to the end for the grace that is to be brought unto you at the revelation of Jesus Christ; As obedient children, not fashioning yourselves according to the former lusts in your ignorance: But as he which hath called you is holy, so be ye holy in all manner of conversation," (1 Peter 1:13-15).