Christians often talk about how "family" is everything, but usually what they mean by this is the family they were physically born into. Biblically speaking, we need to keep two things in mind. First, family is not "everything." Jesus is! When one says, "Family (physically speaking) is everything," then this may show an idolatrous attitude towards our physical relationships. Second, after Jesus, our spiritual family comes #1, not necessarily our physical family. The blood of Christ that joins God's people together is thicker than water, or better, the blood of Christ is thicker than the blood of physical relation.
It is surely a blessing whenever our physical family contains disciples of Christ, but even when that is the case, we need to be careful not to neglect the rest of the family God has given us in Christ. Often our physical family can lead us to forget that the LORD calls His people to work for, nourish, and support more than just our physical family. We should not do one to the neglect of the other, and we need to be careful not to make those who are members of the Christian assembly we associate with feel like "outsiders" because of the emphasis we put on physical family. This happens often in local congregations. Some of our Christian family members can end up feeling all alone because other Christians only make time for the physical family who are in Christ.
“So then, as we have opportunity, let us do good to everyone, and especially to those who are of the household of faith.” (Galatians 6:10, ESV)