Yes.
I'm asking why you think you are black because race isn't something we choose but is rather given to us by the society we live in.
I'm assuming you are of African descent. If so, then you know your ancestors never called themselves black. In Africa people were just whatever ethnic group or tribe they were. Nobody who is today categorized as "black" chose to be black. It was a designation put upon us by Europeans when they started to colonize and enslave the planet. They created the concept of white supremacy and race as a moral justification for their immoral actions. Similar to how some use religion as an excuse for committing mass violence.
Since you are "black" because of white supremacy, then so is Meghan Markle and any other "half breed" because white supremacy didn't differentiate that much between people who were of exclusively African ancestry versus those who were of partial African ancestry.