They go to school and go on playdates and even have sleepovers with their grandparents. (attachmentparenting.org)
Last night, my daughter had a sleepover at my parents house which meant DATE NIGHT! (fitrunningmama.com)
They do also love the prospect of having a sleepover in each other's bedrooms (thank goodness they have trundle beds available). (boorooandtiggertoo.com)