John is strongly affirming that every born-again person has a sin nature. Anyone who denies this fact is self-deceived. Others make the mistake of trying to suppress the old nature by observing sufficient rules. Such a law principle is doomed to failure because it depends for strength on the very flesh from which it seeks deliverance. He cannot become unborn.
Relationship is by birth.
Always has to do with our salvation and relationship in Christ. It can change daily and has to do with the daily walk of the believer. We can lose fellowship, but never relationship. Anyone that believes otherwise is trying to add works to his salvation. God says that salvation is a GIFT and not of works.