If two people possess the same item, put the apostrophe + s after the second name only. Example: Cesar and Maribel’s home is constructed of redwood. However, if one of the joint owners is written as a pronoun, use the possessive form for both.

Use the apostrophe + s after the second name if two people possess the same item. Otherwise, use an apostrophe after each name. Never use an apostrophe with possessive pronouns: his, hers, its, theirs, ours, yours, whose. They already show possession. This book is hers, not yours.