His only appearance in the film is in a flashback when Samson reveals to Ryan that he wasn't born in the wild but, in fact a circus. Before this confession, Benny the squirrel was the only one Samson ever told about his dark past.
In the flashback, Samson's father is shown to have been very strict with Samson when he was a cub and one day he set him out to roar for the audience at the circus but Samson was only able to make a squeaky growl when trying to roar back at the mechanical wildebeest to impress the audience, which caused the audience to laugh at him. After this, Samson's ashamed father told him if had been born in the wild he could have roared before allowing his son to be sent to the zoo after disowning him. It is unknown what happened to him afterwards, though he might still have been working with the circus or have died of old age before the events of the film.
Surrounded by Kazar's predatory wildebeests, Ryan deems Samson a good father, a stark contrast compared to the one his grandfather was.