One has transference to a certain extent with everyone one meets. The closer the person is to other life situations (like you point out with parent child pair being about the same age apart as therapist client) the more possibility I think there might be for a strong transference. But, with therapist and client, I think that's a good thing because most of my problems were during my early years where there was/was the need for, more intense parenting but transference is a very personal thing. My T was not that much older than I was and was a different nationality and background from mine and still, we had a good working transference.