Is essential information: it identifies which of my two (or more) brothers I'm speaking of. This is why no commas enclose Bill . Nonessential words, clauses, and phrases that occur midsentence must be enclosed by commas. The closing comma is called an appositive comma. Many writers forget to add this https://bbs.pku.edu.cn/v2/jump-to.php?url=https://www.autofreshshop.com/