This is such a common problem – I have a lot of people telling me that their kids won't sleep in their own bed and they're constantly coming into their parent's room. If you don't mind and it works for your family then that's great! However, if you are like many of my clients and feel that everyone would get a better night's sleep if there were no nocturnal bed visitors then the tips below might help you address the issue.
Spend time during the day talking to your child about how important it is that they stay in their own bed. It can help to have them repeat it back to you so that you know they've really heard and understood you.
If you've grown so used to kids sneaking in you should consider putting a bell on your door so you wake up when they're on the move. The best time to reinforce the new plan is when they're in the process of moving rather than when they're already snuggled up with you.