Don't sell it, flesh it out before making it an heirloom
What you have here is the potential of having a guide inextricably tied to the party, at least early on.
Depending on what Red wants their father to have been there's some knowledge the other party members can glean from him at their need, or rather have the father reach out whenever you (as GM) feel the party is stumped or stuck at a point they shouldn't be.
A scholarly father may be of some use in exploring dungeons, learning about exotic flora and fauna.
A handyman may be able to point out weak points in a door the party was unable to pick, giving them another means of getting through.
The only thing that might become a problem is Red's desire to be completely oblivious. You should discuss this thoroughly with Red first and the rest of the group second. Unless Red has something manipulating their mind to affect them in a way that makes them incapable to commit anything their father-ring does and is I'd say Red would get very confused very quickly about how the party ends up with certain bits of intel or ideas, especially if the ring hears what's uttered around it and only uses message for his own means expression. Red would invariably question the party's habit of seemingly talking to someone Red can't perceive nor hear them responding in any way.
From your end, I'd consider making the functionality of the ring somewhat like this:
This ring is the gift of some arcane creature or person, having granted a father's wish of being able to be with their child after death. It has already served that purpose for many generations. The latest deceased parent in posession of the ring becomes the new host of the ring, becoming aware of their surroundings whilst worn by their direct offspring. The parent stuck inside the ring can telepathically communicate with creatures near it (5-10-ish feet maybe?). In what was probably a delicious practical joke for the creator of the ring the parent cannot communicate directly in any way with their child.
Additionally, the child wearing the ring has empowered nostalgic feelings towards the ring, parting with it only in extreme circumstances. There seems to be no actual way of making the child aware of their parent's presence and exact words.
The last part should likely not be disclosed to Red or any party member from the outset. They should discover the properties and the origin of the ring during the campaign, if they wish.