A compound subject includes two or more nouns (or pronouns, noun clauses, or noun phrases) and may be singular or plural. When the nouns are joined with the word and (an apple and a banana), the compound subject is usually plural, even if the individual nouns are singular. A plural subject requires a plural verb. On occasion, a compound subject uses two nouns to describe one singular subject (spaghetti and meatballs, my sister and best friend).
Jack and Jill wants more water.
Jack and Jill want more water.
Henry and James is coming to the picnic.
Henry and James are coming to the picnic.