Here’s a quick but useful apostrophe rule that’s good to be familiar with.
If two people possess something together, consider them a single unit and place the ‘s after the second person’s name. Here’s an example:
Rick and Janet are married. Rick and Janet’s new couch was extremely comfortable; that’s why they purchased it.
Alternatively, if two people possess something individually (rather than jointly), each name gets the ‘s. Here’s an example of that:
Sophie and Anna are best friends. Sophie’s and Anna’s couches came from the same store, but they paid different prices.