It happens quite a lot. Counter transference is more common than people think and often if a t doesn't get the right supervision ir support it can lead to ruptures or eventual termination due to their own attachment and lack of awareness around that attachment.
It is only natural for therapists to feel attached or to like some clients more than others. This is where boundaries will either loosen or tighten depending on which end of the counter transference they are in. It's very intimate work they do, they are only human too with feelings and emotions.