This is a very hard issue for both parents and kids. And there isn't a "one size fits all" answer. Jill Fein advises single parents to listen to their instincts. "If you aren't ready to field questions about having your new partner stay over and feel uneasy about the situation, don't issue the invitation."
Many single parents avoid having an overnight guest until they've been with the person for several months, when their children are comfortable with him or her, and when they expect the relationship to be long term. "Instead of confusing children, opt to having your overnight somewhere else," says Brook Noel, the co-author of the Single Parent Resource. "Consider a weekend getaway, or staying at your partner's residence on a night the children will be with their other parent. It's okay to have your partner over and stay late, just try to avoid your children wondering 'Who's in the shower?' or 'Who is sleeping in your bed?'"
No matter how well everyone is prepared, there will be some uneasy feelings the first time you expose your kids to your love life. They may ask you some surprising questions. Depending on their age, your kids may want to know whether you and your ex slept together before you were married, whether you were monogamous in your past marriage, or how many partners you have had. Be honest, but also be appropriate; base your answers on your child's age and level of maturity. "Remember that your children will take your example whether or not they're already dating," says Shelley Joffe. "You don't want your actions to come back to haunt you when your kids begin to date." Teens, especially, may be looking for reasons to say "no" to peer pressure, so make the answers to their questions constructive for them. But also remember that while children should know the basics of your social life, they do not need graphic information about your sex life.