From our panel of staff contributors
You draw boundaries. (Early on would be best!) We are all a family, but we all need our own space; each of you is not allowed to enter the other's room or use the other's items without permission. As much as we enjoy each other's company, we also get to have time with others, by ourselves. If these boundaries are established and respected, then they should leave each other alone when entertaining a friend in his or her room. Jealousy that may lead to hurt feelings can possibly be avoided if both invite friends over at the same time, so each has something to do without the other.
I'd make sure the sibling with the guest isn't doing/saying anything at the other sib's expense (which can happen when there's a new person in the room to impress). Otherwise I'd be firm in telling the (temporarily) friendless sib that "jealous or not, your brother/sister gets to have friends over sometimes, and you get to butt out." And then I'd do what I could to keep the sib left out from feeling completely abandoned.
First, how not to deal: By forcing the sibling who has a pal over to include the sibling who doesn't.
"As the parent, you need to help your child tolerate and bear the fact that sometimes they are not going to be included," says family therapist Fran Walfish, author of "The Self-Aware Parent: Resolving Conflict and Building a Better Bond With Your Child" (Palgrave Macmillan). "They're not always going to be invited to every birthday party or make it on every team.
"The only way to equip them with the coping skills to deal with inevitable disappointment is to allow them to struggle with a letdown, with you right by their side."
Comfort the jealous sibling, Walfish says, by telling him or her, in an empathetic tone, "It's hard to be left out. But everyone needs friends of their own."
Then suggest a way to pass the time that doesn't include pestering the sibling and her pal: Setting up a simultaneous play date, enjoying some mom or dad time, diving into the toy closet without the burden of sharing.
Encouraging your kids to develop and nurture their own independent friendships will keep up the already-harmonious relationship longer than giving in to the whims of the jealous sibling.
"Forcing one child to include the other fuels natural, normal sibling jealousies and rivalries," says Walfish. "And worse, it keeps the other child from exploring their own internal resources for developing social relationships."
It's better to foster an environment in which siblings take a break from playing together to make plenty of room for nonfamily fun. "Then each child comes back enriched individually from having a friend of their own they can share stories about," says Walfish.
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