Here's what happened to Alex and Nicky Katsopolis (Dylan and Blake Tuomy-Wilhoit) in Fuller House, and why they weren't in the series finale. Aside from seeing DJ (Candace Cameron-Bure), Stephanie (Jodie Sweetin), and Kimmy (Andrea Barber) walk down the aisle and marry the loves of their lives, the Full House spinoff finale also doubled as a reunion for the Tanner extended family. That said, there are some notable absences, including Jesse (John Stamos) and Becky's (Lori Loughlin) twins.
Debuting in Full House season 5, the baby boys replaced a different set of twins who were initially cast to play the Katsopolis kids. Nicky and Alex's introduction came at a point where Michelle (Mary-Kate and Ashley Olsen) was old enough to become an older sister figure to her cousins. The family sitcom thrives with child-focused narratives, so bringing a new set of babies in the show was a great way to continuously cover that base as the Tanner girls grew older. While Nicky and Alex didn't come close to Michelle's prominence, they were integral parts of Full House, enough for Fuller House to bring them back in the first season.
In Fuller House season 1, Nicky and Alex were back in the Tanner household with their parents as they supported DJ following the sudden death of her husband. Unfortunately, the once smart boys turned out to become shallow men - at least that's how they were depicted on Fuller House. Jesse constantly made comments about their lack of direction in life, with their mom a little bit more understanding. Apparently, however, the twins had a plan - open a fish taco food truck after finishing college. Alex and Nicky returned in Fuller season 2 during the Thanksgiving episode but never again after that. The last fans heard about them, Kimmy confirmed they indeed pushed forward with their plans, with the pair living in their truck. Still, with the wedding of their cousins, fans expected them to show up in the Fuller House finale - but that wasn't the case.
Nicky and Alex weren't at the wedding, and there wasn't any word on whether or not they were invited to the party. That's despite Jesse being present during DJ's engagement, the family's Thanksgiving dinner, and the wedding itself. He even visited the house on a random day following Pamela's biting incident at school, and yet, he never talked about his sons. Fuller House explained why Becky's not around - working around their way on Loughlin's firing from the series following her involvement in the national college admission scandal; however, the whereabouts of her twins weren't mentioned. Perhaps leaving the boys out of the finale was an intentional creative choice as to not highlight the fact that Becky isn't at the wedding. Jesse didn't say, but maybe even the boys are in Nebraska with their mother and grandmother.
Behind-the-scenes, there's also the possibility that an appearance from the Katsopolis boys for the Fuller House finale was in the works but just didn't push through. It's worth noting that Dylan and Blake are no longer actors, although both are still working in the entertainment industry. Dylan is an acclaimed foley artist, winning three Emmys for his post-production work on Game of Thrones. He also worked on Death Note, Jack Ryan, and Castle Rock. Meanwhile, Blake has joined the family audio engineering business, but also does video game streaming on Twitch.