I haven't but if you are all comfortable with each other and you are all responsible it shouldn't be a problem. Just make sure you discuss the logistics like bills and chores and groceries. Nothing ruins a relationship faster than money and maintenance.
"Regret for the things we did can be tempered by time; it is the regret for the things we did not do that is inconsolable." - Sydney Smith
Kyle: 27 year old male
Katie (rymmare): 25 year old female
Kids: girl: 5 years old, boy: 3 years old