Is it selfish to not want to move in with a boyfriend whose live-in mom is old and sick?

Relationships encompass the family of another; if the mother WAS a problem, she will be again. If I were in a relationship now, while caregiving MY mother, I would have to end it. My mother would do whatever she could to thwart the bond with my significant other. She has done it in the past, anytime she could get her nose in close enough. You know in your heart how to deal with this...

Here's some tough love. RUN! 15 years is enough distance for it to seem like it would be nice to restart a romance, but stop and think about it. His mom is in poor health so she will always come first in the relationship. Since you live in different countries, you might try dating for a while to see how the three of you will actually get along. With failing health comes the return of old issues and the two of them bonding more. Are you willing to be the third wheel of a couple? But if you do move in, you cannot use her as a weapon every time you feel resentful. You knew this was coming before you committed to this relationship.