Does Kate have to drink milk every day? - No she doesn't
Do Kate's brothers have to to drink milk every day? - Yes. they do
Did Kate have to go to bed late yesterday? - Yes, she did
Did Kate's brothers have to go to bed late yesterday? - No, they did not
Did Kate have to go to the doctor yesterday? - No, she did not
Did Kate's brothers have to go to the doctor yesterday? - Yes, they did