The big question on This Is Us is who Kevin will end up with in the future — assuming that he does fall in love again and find someone to settle down with. While many people speculated that the person Kevin ends up with is Cassidy, the veteran he met while visiting his Uncle Nicky in Bradford, an earlier episode in the show's final season seemed to shut that theory down. Cassidy told Kevin that he was "chasing the wrong blonde in the wrong city," implying that the two simply weren't meant to be. However, Season 6 episode "The Guitar Man" revealed that just because Cassidy and Kevin aren't endgame, doesn't mean she isn't a big part of his future.
Last season's flashforward to Kate's second wedding showed Kevin holding a note with the logo for "Big Three Homes" on it. Kevin's father Jack always wanted to create his own construction company, called Big Three Homes, but never got around to it — he died when his children were just teenagers. While Jack couldn't make Big Three Homes a reality, Kevin did just that in "The Guitar Man" upon realizing that he could hire veterans who had a ton of construction experience to build homes.
Cassidy ultimately served as the inspiration for the company. In the episode, Cassidy goes out for a late night drive, and ends up driving head-on into a pole. While she wasn't explicitly trying to end her life, in that moment, she essentially just gave up and gave in to sleep, having suffered intense trauma from her time in Afghanistan that made a good night's sleep elusive.
Kevin realizes that Cassidy was just one of many vets — including his Uncle Nicky and the vets Cassidy hired to work on the Pearson family cabin — who were struggling after returning to the United States. Instead of ending his construction project with the single Pearson cabin, Kevin decides to create Big Three Homes as a way to employ these people, in honor of his father's legacy.
It's unclear how involved Kevin will be in Big Three Homes. He is, after all, still an actor who is currently working on The Manny reboot. He also has a home in Los Angeles, and twins he shares with the California-based Madison. While Kevin may not have his boots on the ground 24/7, it's clear that Big Three Homes will be a part of his legacy — something that gives him the purpose he has been searching for all these years.