Concept:The subject is singular because the phrase “with his wife and children” only adds extra information.The main subject is “My brother”, which takes a singular verb.Explanation:The phrase “with his wife and children” is set off by a comma and is not part of the subject.So the verb must agree only with “My brother”, which is singular.The time is “next weekend”, so the present continuous form is is correct.Thus, singular is is used instead of are.Answer:B. is