Require siblings to be a role model. As people enter adulthood, they automatically (though not always willingly or positively) move into the position of being an example to others. That is particularly true for members of a family or community. Make it clear that all older teens are expected to be a role model to any younger kids. The youngest or single kids should be a role model to younger neighbors, cousins, family friends, etc.
Use cooperative punishment. Siblings that misbehave together should suffer together. A great punishment for siblings who are having conflict is to make them complete tasks together. If they argue at all, keep adding tasks until they are successful in completing them without rancor, bitterness or conflict. You can even require them to be formal and sarcastically polite to each other as part of the punishment (e.g., “Thank you dear brother. I would be ever so grateful if you would hand me that cleaning device.”). Any deviation from cooperation and pleasant mutual support will result in an additional task. Repeat until they are successful or your spring cleaning is done.
Parent’s little helper. One strategy for teaching your kid how to deal with their sibling (especially a younger sibling) is to mentor them with direct instruction. Consider setting aside some time when your kids have to engage in a cooperative task while you are in attendance. This will give you the opportunity to directly intervene and redirect their behavior before it careens out of control and into a major conflict. This allows you to use direct instructions for how they should act or respond, do-overs and questions that require them to consider the impact of their behavior on their sib.
Make time for each child. Kids can be very sensitive to fairness, especially when it comes to getting time with parents. One source of conflict could be resentment or competition for you time and attention. Be sensitive to whether you have given each kid a clear period of individual time, even if it is just 15 or 30 minutes. Make it clear that you are focused on the child you are with both by not multi-tasking and by redirecting your other kids (“I’ll be with you in a minute. This is my time to talk your brother.”). Individual time is particularly important for siblings of a special needs child (whether it is due to physical or mental challenges or personality).
Shop for presents. Sometimes being thoughtful and considerate needs to be taught. Have your kids get something for their brother or sister on their birthday. Start several weeks before the event by reminding them of the need to acquire the present. They will probably need help trying to think about what their brother or sister might want. Require them to really think about it. Help them out with questions that might lead them to an answer. Prep the gift recipient on how to be gracious when accepting a present. (And, let the recipient know that insufficient graciousness and gratitude will result their misery and suffering for them.)
Family motto. Create a motto for the family that emphasizes cooperative, familial bonds. Families always stick together. We take each other’s back. We protect each other’s reputation. Family information is private. You can always count on family.
While some siblings seem to naturally connect and bond, many others, if left to themselves, will spend their time just annoying the devil out of each other until they move out of the house. The more you actively guide and shape how your kids treat each other the better prepared they will be to deal with the people who share their lives (e.g., room mates, spouses, coworkers, etc.).