Question: how are dr grey and dr pierce related
[{'answer': 'maternal half sister', 'provenance': [{'wikipedia_id': '7687013', 'title': 'Meredith Grey', 'start_paragraph_id': 27, 'start_character': 29, 'end_paragraph_id': 27, 'end_character': 49, 'bleu_score': 1.0, 'section': 'Section::::Storylines and Characteristics.\n'}]}, {'provenance': [{'wikipedia_id': '7687013', 'title': 'Meredith Grey', 'start_paragraph_id': 27, 'start_character': 0, 'end_paragraph_id': 27, 'end_character': 606, 'bleu_score': 0.9642618757124931, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15409598154661545855}, 'section': 'Section::::Storylines and Characteristics.\n'}]}]