Sentence 1: My sister-in-law B was driving out yesterday afternoon. 
 Sentence 3: B's daughter wanted her to pick up both of her kids, aged 12 and 9 
 Sentence 4:  B refused, as the siblings fight a lot 
 Sentence 5:  B picked up the younger kid and the other stayed in after school care 
 Option 1: She was picking up one of her grandchildren from school. 
 Option 2: She was picking up her 12 year old twin grandchildren from school.