Theuns, 26, stepped up to the WorldTour with Trek in 2016 after a standout 2015 season with the Belgian Topsport team, in which he finished second at Dwars Door Vlaanderen and Scheldeprijs. He produced a string of encouraging performances last year, notably in sprint finishes, but his progress was halted when he fractured a vertebra on his Tour de France debut.
A long recovery progress ensued but he has bounced back this season, with a top-10 at Paris-Roubaix and a first WorldTour win earlier this month in a BinckBank Tour sprint.
"I am very happy to join Team Sunweb. I have gotten to know the team during our talks over the previous years and I feel like now is the right time to make the move across to Team Sunweb," said Theuns.
"The most important reason for my decision is how the team operates and how they strengthen their riders to bring them to a higher level. Together with the team I hope for many successes, with a focus on the Flemish races. On top of this, our goal is to add strength to the lead-out and develop my sprint further, which I feel like is entirely achievable with fast men around me and the knowledge within the team. I am confident I can make the next step in my career at Team Sunweb."
Sunweb directeur sportif Marc Reef added: "Edward is someone who we have been following for quite some time and we are really happy to start our cooperation. He is a strong classics rider who we believe can take steps forward when working within the team's structure. He will be our leader in the Flemish classics and his power will be of added value to the team's sprint train."
While Theuns will be deployed across sprints and classics, Vervaeke, 23, will continue his development as a stage racer at Sunweb.
The Belgian turned pro with Lotto Soudal after a quality 2014 season in the U23 ranks, where he won the Ronde de l'Isard, the Tour des Pays de Savoie, and a stage of the Tour de l'Avenir. The start to his professional career, however, has been a troubled one, with a long list of crashes and DNF's, though he did show his potential with 11th overall in a stacked field at the 2016 Vuelta al País Vasco.
"I am thrilled to be joining Team Sunweb for the next two seasons. Their success through this season has been brilliant and I'm excited to play a part of that for the coming years. In the mountains I want to be of added value and hope to learn a lot from the current GC riders in the team," said Vervaeke.
"I feel that this challenge, way of working and professional structure at Team Sunweb is precisely what I need and I am very pleased with the opportunity. My first aim will be to come back up to my previous level after a year with bad luck and then I hope to show my full potential. I am very much looking forward to pulling the jersey on at the start of 2018.”
Reef added: "Louis has already been professional for a few years and is still very young at only 23 years old. He will strengthen our GC squad bringing crucial support and and we want to work together with him over the coming years and continue to develop his strengths on the climbs and GC to grow step-by-step to go for the classification in the future himself."
Theuns and Vervaeke are Sunweb's second and third signings of the transfer window after Martijn Thusveld joined from Roompot. Warren Barguil, Ramon Sinkeldam, Georg Preidler, and Bert de Backer are all leaving the team.