The relationship between Finn Hudson and Jackson Whittemore is greatt and on good terms. They probably knew each other when Jackson was joining the Slytherin Quidditch team as they are both Seekers. So they probably met official somewhere in 1992. With Finn being the captain of the Hufflepuff Quidditch team and Jackson being captain of his team, they both meet each other often to plan how to destroy the Gryffindor Quidditch team, since they both wanna make sure that they don't win the House Cup. Besides their Quidditch experiences, they greet each other in the hallways and seems to be on good terms.
Their friendship became official ever since Finn knows about his relationship with his little brother Brody. When Brody told Finn about his sexuality, Finn supports both of them and their relationship. Finn and Jackson became closer and they both like to drink at Hogsmeade to get to know each other a little better. Jackson visit the Hudbar household to celebrate the holidays and to have fun together.