Fuller House's final season attempted to introduce Kimmy Gibbler's parents, but it only inadvertently caused a plot hole for Full House. Not much is known about Kimmy's (Andrea Barber) family. In fact, it was only during Netflix's sequel spin-off that fans learned of her brother, Jimmy (Adam Hagenbuch), who eventually married Stephanie (Jodie Sweetin). As the siblings geared up to tie the knot, Joey (Dave Coulier) attempted to get their parents involved, setting up for their anticipated introduction.
With Mary-Kate and Ashley Olsen refusing to reprise their joint role as the youngest Tanner sister, Michelle, Fuller House worked around her absence by bringing in Kimmy to essentially take her spot. After the death of DJ's (Candace Cameron-Bure) husband, which kicked off the events of the sequel offshoot, she and Stephanie moved in the Tanner family home to help her newly-widowed friend raise her three sons. As one of the lead characters of Fuller House, she's become the focal point of many storylines including the midseason 5 premiere.
The Gibblers were excited at the prospect of having Mr. and Mrs. Gibbler in town since their parents have yet to return home for two decades. Apparently, they left San Francisco to travel around the world in the hopes of locating lost cities. From her and Jimmy's comments, it also didn't seem like they're in constant contact with them as Kimmy claimed that they haven't met Ramona (Soni Nicole Bringas) or learned about her business. To further emphasize this point, she added that her parents have not even seen her with straight hair. The problem is, considering how long they're supposed to have been gone, that's not the case.
In the final season of Full House, which took place in 1995, Kimmy primarily wore her hair long and straight. Granted that she styled her mane in crazy curly ways from time to time, including how she did it for her and DJ's prom night in the finale, during normal school days, she typically left it down. In fact, this was also the case in seasons 6 and 7. Given the timeline Jimmy gave, it's impossible for Mr. and Mrs. Gibbler to have not seen their daughter with straight hair before they left to travel around the world.
Kimmy's family background is riddled with a lot of inconsistencies. At one point in Full House, she said that she's the youngest of three sisters, and after her, their parents didn't want to have kids anymore. Yet, there's Jimmy, who's around the same age as Stephanie, meaning he should already be born around that time. The changes in Kimmy's family information may have something to do with the fact that she wasn't supposed to be a prominent character in the original '80s/'90s family sitcom. She was originally going to appear once only. but after the positive response from the viewers, the show producers decided to expand her role. It would've been for the best if Fuller House didn't try to delve into this particular subject matter since it's most likely only going to further muddy the continuity evidenced by this newly created plot hole.