Is ‘s or s’, has, is or the possessive’s/s’? Write as in the example

Certainly! Let's look at each sentence: 1. Ken's brother is in the car. - Possessive: Ken's 2. He's got a noisy dog. - He is: He's 3. She's my grandma. - She is: She's 4. That's Carl's idea. - Possessive: Carl's 5. She’s got the boys’ notebooks. - Possessive: boys' 6. Amir's Tom's best friend. - Possessive: Tom's 7. Helen’s mum is the girls’ aunt. - Possessive: Helen’s, girls'