Long story short, Harland discovered the rogue group's activities from the twins. That's why Harland approached Desmond only to save the two without revealing that he knew the boys.
Until one day, Kellam appeared and took over the group of rogues by challenging Desmond and defeating him. Kellam didn't know the boys nor care about them, especially the useless ones.
Neither noticed nor caught the twins when they saw an opportunity to escape by shapeshifting. The two immediately contacted Harland and told him what had happened.
This incident only happened a few months ago, and two weeks before the rogue group attacked Orteaux, Harland met the boys and evacuated Sabertooth to safety.
From the story of the twins, everyone could see that Harland didn't want to involve his pack and only brought his Beta and Omega to join his rebellion.
