If I had a $1 for every time someone brought up a myth connected to bloodlines......
While genetics has proven that certain traits can be emphasized within a certain linneage, most people actually forget that those bloodlines actually had to come from somewhere, start from something. In other words, even if your great-great-great-great-great grandmother, all the way up to you, have been witches, there had to be a grandmother somewhere back there who didn't know an herb from a vegetable.
In my opinion, bloodlines are overrated. Some of the worst witches out there have documented bloodlines, which just goes to show that talent is the result of hard work as much as anything.
As for it being a 'curse', that's someone pulling your dramatic leg. Curses and magickal powers are the plots of books and in the minds of authors who wish for things. You obviously know this person doesn't know their butt from a hole in the ground so don't worry.
"it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing."