When you have siblings, no matter if they get along or not, it's a wise choice to help them foster a close-knit relationship so they can communicate effectively. For general sibling bonding, conducting a few team building exercises can be a fun way to achieve your goal. Create fresh, simple activities that will not only engage them, but do the job of building their team as siblings.
A dynamic way to start siblings well on their way to bonding and building as a team is to send them off on a scavenger hunt. Plant several clues that lead to subsequent clues and ultimately to the finish line where there's a prize. If you have four or more kids, break them up into teams to work together, perhaps matching those that normally wouldn't pair together, like an older brother with the youngest sister or two quarreling sisters. Make clue cards that somehow relate to family tidbits, such as "Aunt Sarah left this item behind when she ventured off on her honeymoon cruise with Uncle Bob." A clue like this may lead to Aunt Sarah's coat hanging in the closet that has another clue in the pocket.
Story Telling Grab Bag
Use a pillow case to serve as a grab bag. Take multiple items from the siblings' possessions such as a teddy bear, souvenir or toy. Fit as many items in the grab bag as you can. Have each sibling take turns pulling an item out of the bag. Ask them to work together to form a sentence or two using both elements pulled and write them down. If a teddy bear and a pair of sneakers were pulled, challenge each sibling to be as creative as possible. For example, the siblings could form a beginning sentence, "Once upon a time a teddy bear put on blue sneakers and ran through the park." After all the items are accounted for, have them work together to arrange the sentences together to form a complete story. You can extend this project by assigning them to create an illustration or storybook of the tale and share it at a family gathering.
Set up an obstacle course in the backyard or open park ground. Lay down hula hoops and a jump rope; gather as many things that can be used for the sibling to navigate over, around and through. Once the obstacle course it set, blindfold one of the siblings. Allow the other sibling to serve as the guide, providing detailed directions to lead the other through the course. For example, "Walk three steps forward then turn to the right. Hop forward once." Reward the siblings for working together, even if they don't quite make it through the course properly.
Set out a bunch of photos of the entire family. Go back as far as you possibly can from great-grandparents to newborn cousins. Challenge the siblings to work together creating a family tree using an oversized poster board, markers and spray glue. View the finished product and sit the siblings down to tell a little story about the family.