Howland Reed is the Lord of Greywater Watch, the southern-most hold in the North. He is among Ned Stark’s oldest and most trusted allies, fighting alongside him during Robert’s Rebellion and bearing sole witness to the true events at the Tower of Joy. Though there is some speculation that he may have been amongst the noble characters during the election of the king in the final episode, Reed is yet to make an official appearance within the present timeline of the franchise.
Fans of the series long theorized that it would be Howland Reed who would reveal the secret of Jon’s parentage, an honor that was ultimately granted to Bran as the Three-Eyed Raven. Beyond appearing in the flashback at the Tower of Joy and sending his children to aid Bran, Reed made little to no impact on the story at large, which seems unusual for a character of such presumed importance. Although the fan theory certainly cannot come to fruition at this point in the narrative, a Jon Snow series set north of The Wall could finally properly introduce the character and give closure to his family’s story.
Meera Reed was featured prominently for several seasons before being sidelined after Bran’s return to Winterfell, ultimately returning to her home at Greywater Watch. Jojen’s body remains north of The Wall, and as a son of a Northern lord, it would likely be customary to have him buried in the crypts beneath the city. Having Meera lead her father and his men on a journey to retrieve Jojen’s body would be a fitting way to close out House Reed’s story and would set up a long overdue conversation between Jon and Howland.
Although much of the events leading up to Lyanna Stark’s secret marriage and eventual death have been covered to varying degrees throughout Game of Thrones, there are still some murky details regarding the months that followed that could be cleared up through Howland Reed’s recounting of the story. But perhaps most importantly, Howland Reed's inclusion in a Jon Snow series would add a degree of depth to more stories than just his own. Ned Stark’s last promise to Jon was that he would one day return to tell him about his mother, and having Howland Reed take on that responsibility in his stead would make all three of their stories richer and more complete.