Elizabeth.
Luke tells the story of Mary's visit to her relative Elizabeth in Luke 1:39-45.
Bonus: That child was John the Baptist.
Above is a painting of the visit by Carl Bloch. Notice how old Elizabeth looks--well beyond child-bearing years. The angel Gabriel, when he tells Mary that she is to bear a son, also tells Mary that Elizabeth is pregnant "in her old age." This is found in Luke 1:36. Only Luke tells us about Mary's visit to Elizabeth.
