…maybe. Though Benjen was at least an active part of the story in the first book, whereas Gerion has only appeared in memories.
Also I’m not sure “a softer approach to the family legacy” is exactly the right comparison. Their motivations, actions, and the attitudes of the rest of the family, are all very different.
Gerion felt it was “better to mock the game than to play and lose,” so made jokes rather than compete with Tywin. His trip to Valyria to find Brightroar might be considered supporting the Lannister legacy, but Tywin considered it a “fool’s quest”. And it’s true he never married, but he also left at least one bastard for the family to support.
Whereas Benjen… per GRRM, he was the Stark in Winterfell during Robert’s Rebellion, and left for the Night’s Watch shortly after Ned came home with Jon (and Catelyn and Robb). The Starks have always been friends of the Watch, and many younger sons have been members… although he may have had a more personal reason to join. Benjen never married, but he also joined a celibate organization that supports the realm altruistically.
So it’s sort of a parallel… but also very much an “adventurous third son” fairy tale trope with lots of differences when you come down to the details. But if we ever find out what happened to either one of them, maybe we’ll find more parallels, and we’ll be able to see if it’s something GRRM deliberately did or if it’s just a coincidence.