How should we view teasing amongst siblings?
Dr. Joel Beeke explains in this video that when it comes to sibling relationships, it is wise to examine how much they should be allowed to tease each other. This is a difficult question to answer.
In every family, there will be a certain measure of teasing. The mother and father can do a lot in setting the tone for the home. Cruel teasing should always be out of bounds, as that is sinful. However, lighthearted teasing, where no one's feelings are hurt is normal.
Ephesians 4:29 (NKJV) - "Let no corrupt word proceed out of your mouth, but what is good for necessary edification, that it may impart grace to the hearers."