A little something I bet you didn't know

My grandmother, my father's mother, was very fertile.
She had three sets of twins.
The oldest set were two boys with one dying in infancy.
The second set was a set of stillborn girls.
The third set was my father and a stillborn girl.
So if you add those four to the nine children that she had that lived you have thirteen kids, and I'm not sure, but I think she may have had one or two other stillborn babies, and do they still use the term stillborn?
I think I would have made a great twin.