The correct option is (c) is
When two subjects are joined by "along with," the verb agrees with the first subject ("his brother"), which is singular, so "is" is used.
"Along with," "as well as," "together with," etc. are not conjunctions — they don't make the subject plural. The verb always agrees with the subject before these phrases. Here, "his brother" (singular) is the main subject, so a singular verb "is" is correct.