You're the one who gets to decide what to do with your training. I know, as a professional who has done a bazillion hours of volunteer work, that it's very hard for some of us to charge what we're worth, especially after setting a precedent of giving our work away to friends or family. Ouch.
If I were in your position, I would say in a relaxed and friendly tone, "Jean, I'm glad you and your daughter have been finding my skills beneficial. And I'm just not comfortable continuing with free massages – I have other priorities I must pay attention to. I am willing to offer you special family rates (name what your time is worth to you). Would you or your daughter be interested in continuing?"
If Aunt Jean has any sensitivity at all, she'll take this switch graciously and express tremendous appreciation for the free time you've given her so far. If not, she may act startled or even say something rude. That's on her, not on you. But you really must be the one to change the situation if it's going to change. I don't know why, but once you act like it's a pleasure to give yourself away, some people will happily keep asking for more.
And please RESIST the urge to make excuses or offer explanations, or to apologize for a necessary change. It is your right to value your time, training and energy. Those strategies just open you up to arguments and wheedling. Be calm and professional, and as inevitable as the tides.
You can do this. Practice with your husband, or a friend, or in a mirror until you can just state your new needs and expectations clearly, calmly, and with a smile in your voice. I wish you the best.