Short Answer 
Kaitlin Olson is not related to Mary-Kate and Ashley Olsen, despite the similarity in their last names. Kaitlin is known for her role in *It’s Always Sunny in Philadelphia*, while the Olsen twins gained fame from *Full House*. Their backgrounds and birthdates further underline their lack of connection.
Step 1: Clarifying Relationships
To establish the facts, it’s important to note that Kaitlin Olson is *not related* to Mary-Kate and Ashley Olsen. Both are prominent figures in the entertainment industry but come from different backgrounds. Kaitlin is known for her role in the sitcom *It’s Always Sunny in Philadelphia*, while the Olsen twins gained fame as child actresses in the late 1980s and 1990s.
Step 2: Background Information
Kaitlin Olson was born on August 18, 1975, in Portland, Oregon. In contrast, Mary-Kate and Ashley Olsen were born on June 13, 1986, in Sherman Oaks, California. Their early fame came from their appearance on *Full House*, where they portrayed the character Michelle Tanner, making them household names and setting the stage for their future careers.
Step 3: The Importance of Names
The *similarity in their last names* has led to confusion, but it is essential to understand that surnames can be quite common and *unrelated*. In the vast entertainment field, it is not unusual for individuals to share similar last names, and these could arise from coincidences or even chosen stage names. Thus, the absence of a family connection between Kaitlin Olson and the Olsen twins is clear.