Just chiming in to agree with everyone here

I can't call my T all the time, obviously, and I am very lucky to have close friends I can call when I am having a hard time. I have 4 very close friends that I can call to talk about anything from AA stuff to eating disorder stuff to SI stuff to what's going on in therapy to whatever (obviously, I have such a huge list of issues that the universe had to see to it that I had lots of people to call on lol). Plus, I can talk to my H. Like ktgirl said, I am not paying any of these people a fee to talk to them once a week, with all of the boundaries that go along with that. So, I don't see your relationship with your family member as a dual relationship, I see it as a friendship, or a source of support.

When I need T, I call T. I just talked to him on the phone tonight. I could have called one of my friends, but I really needed my THERAPIST right then.

It's definitely something to explore, especially if you are concerned about it, but to me, it just sounds like a loving source of support that you are lucky to have.