There are people in the world who feel they need to isolate their partner from others for a successful relationship. Much of this behavior is unconscious, but some people do it purposely. They look at the way they are, and they have a need to ensure they will not be compared to others. Rather than make changes in the way they live and think, they seek out a vulnerable person to have for their very own.
There are many ways to isolate a person from friends and family, and someone who has been in multiple long term relationships is often successful at isolations techniques. Many of them begin with small and subtle modifications to the relationship, but some are too impatient to wait long. They begin isolating their partner immediately from the outside world, and they do not stop until their partner's other social or personal connections are lost. This can be a victimless relationship because some people prefer this type of partner.