When they're young, it's fun for siblings to share a bedroom. The pillow fights! The shadow puppet shows! Only if those siblings are boy and girl, many parents agree that this innocent arrangement can't continue indefinitely. How soon opposite-sex siblings need separate bedrooms is a question that sparks heated debate among parents, with some claiming "Hey, I shared a room with my brothers and sisters until college and I didn't mind one bit!" Still, if you're a parent who does wonder how early the awkwardness can ensue, here's an expert's assessment.

"Boys and girls become aware of their gender and physical differences as early as 3 and begin to separate socially from the opposite sex as early as 5 to age 7," says Kate Roberts, Ph.D., a therapist and contributor to EmpoweringParents.com. "In order to respect their independent developmental process, it's best for them to have separate living space, in so far as bedrooms, as young as age 6 or 7. This allows the space for the individuals to become naturally comfortable with their body and exploring themselves without being self-conscious in the presence of the opposite sex."

This isn't just based on her opinion, but dates back to legendary psychoanalyst Eric Erickson's extensive research on children's stages of psycho-social development. It's also from the mouths of the many kids Roberts sees in her practice. "I've heard from opposite-sex siblings in this situation that it's very uncomfortable for them," says Roberts. "It starts around 6 or 7, definitely by age 8." And same goes for twins, too. "Even if they're twins, they're still different genders and that needs to be respected," says Roberts.

Since kids aren't always good as articulating their desire for privacy from family members, try to remain sensitive to their bids for solitude. "Signs to look out for include when one of them locks the bathroom or bedroom door when changing or asks the other to stay out, an increase in comments about the sibling being the opposite gender, or a growing curiosity about sexuality issues, gender differences, or physical changes," says Mark Loewen, a licensed professional counselor at Launchpadcounseling.com. If your living quarters are tight on space and you're reluctant to renovate or move, consider at least putting up a divider so that both can have some privacy.

At what age do you think opposite-sex siblings should have separate bedrooms?