Unfaithful Swine

He cheated on his wife Lily with Creek's mom (whom I'm thinking naming "River Mossbloom" or something).

Lily, being whimsical and lively, optimistic yet down to earth, was a good influence on Pine.

River, being blindly optimistic and averse to anything and everything negative, is a bad influence on Pine.

Shitty Father

He walked out after Lily died and before Branch hatched.

He used to have a close bond with his sons, which started to crumble when he started missing events that were important to their sons and breaking his fatherly promises when he started cheating.

He has been ignoring their existence in favor of River and their son Creek.

He, along with River, raised Creek to always be positive and push away any and all negativity.

When the Great Escape happened, did he change his name? Or did he take advantage of his brethren's collective blind faith that all trolls have good in them and lie about how he lost his previous family to the bergens? Or did he just pretend his sons with Lily didn't exist?

Did he take advantage of the fact that his sons with Lily are missing?

It isn't until Creek's death that Pine wants to reunite with his sons.

If Pine saw them again, he would greet them with open arms as if he didn't walk out on them twenty-four years ago.

He doesn't see the damage he did in walking out on them.

Awful to his unknown fifth son

He looks down on grey trolls. Even believes greyness to be contagious.

When Branch was a kid, Pine felt no compassion for him.

Up until after the events of the first movie, Pine thought him to be a paranoid negative nancy.

When Branch was growing up, Pine, along with River, openly badmouthed him.

Since Branch regained his colors and became the village hero, Pine refuses to acknowledge his mistreatment of Branch, much less apologize.

Nothing here is finalized yet as they are subject to change.