This is an interesting question. Some cultures encourage children to sleep either in the same room or bed as the parents for the first few months or even first year. There is no definitive right or wrong answer to this issue. The question is really about what you (as a family) want. If you don't want your child to end up in your bed, then those limits and expectations need to be reinforced very consistently. Often parents complain about children spending each night in their bed but do not reinforce any alternative. Sheer persistence in helping the child understand that their bed is not your bed, is an important first step if that is what you want. Sometimes children experience fears or nightmares or anxiety. It may be preferable for a parent to sit with the child in the child's room until they fall back to sleep, or to keep a night light on so that the child comes to see there is nothing to fear about their own room. Consistent reinforcement is important in this issue.