Question

these aren't their brothers改为单数句 jack is my brother's good friend.改为一般疑问句，并做肯定回答

is this your sister ？改为复数句

Answer 1

This is't his bother.
Is Jack your bother's good friend? -Yes,he is.
Are these your sisters?

英语要好好学啊……

Answer 2

He is not his brothers;
Is jack your brother's good friend? yes he is;
Are these your sisiters？

Answer 3

This is not his bother.(此处不可用isn't哦)
Is Jack your bother's good friend? -Yes,he is.
Are these your sisters?

Answer 4

This is't his brother.
Is Jack your brother's good friend? -Yes,he is.
Are these your sisters?

Answer 5

This is their brother.
Is jack your brother's good friend?Yes it is