Personally, I don't think most elements of the story are plausible, for a few reasons.
1) Keepers of the Moon are a matriarchal society, as you mentioned. That being said, I'm not sure why they'd choose a male as their leader. Even if there were no spectacular female candidates, I imagine they'd still be just as trusted or at least preferable to any male alternatives. It's not impossible, as we see exceptions with the Coeurlclaw tribe, but iirc that's a case of a male Keeper striking off on his own and taking in misfit Keeper women who are most likely disillusioned by their own clans (and being somewhat held hostage).
2) There's no precedent for the races of man shapeshifting (barring Primals and dragons, and Void related things which are different situations). There's also, of course, therefore no precedent for this to be any sort of inherited, ritualistic thing (an ability that is passed on after its current host's death) and I'm not sure why it would function that way.
3) Saying that if he shapeshifts too much he'll eventually "get stuck" is fine, but it's not much of a trade off for the strength his abilities could grant him. Downsides that are somewhat abstract (we don't know how much "too much" is) and/or far off in the future (we also don't know how long it will be and how much shapeshifting it will take for this to ever catch up with him) don't do well in balancing anything, as they don't tend to affect the person's RP in this current moment and potentially may never crop up in the person's RP at all. It's an okay flavor tidbit for your character, but if your character decides to turn into a tiger and maul someone, it's not a weakness that actually benefits the other player/character in anyway nor one that inhibits your character in that moment. A better downside would perhaps be the transformation being physically painful and taking a notable amount of time, thus leaving him vulnerable and open to attack while shapeshifting.
4) The bit about his father is honestly probably the least unlikely part. Granted, from what was outlined in the OP, we don't have any explanation given for his actions and behavior, which could perhaps raise some eyebrows about why he'd take such dramatic action against his own son for seemingly no reason.
As always, you should of course role-play whatever appeals to you, but if you're looking for lore compliance, I don't think this concept fits.
1) Keepers of the Moon are a matriarchal society, as you mentioned. That being said, I'm not sure why they'd choose a male as their leader. Even if there were no spectacular female candidates, I imagine they'd still be just as trusted or at least preferable to any male alternatives. It's not impossible, as we see exceptions with the Coeurlclaw tribe, but iirc that's a case of a male Keeper striking off on his own and taking in misfit Keeper women who are most likely disillusioned by their own clans (and being somewhat held hostage).
2) There's no precedent for the races of man shapeshifting (barring Primals and dragons, and Void related things which are different situations). There's also, of course, therefore no precedent for this to be any sort of inherited, ritualistic thing (an ability that is passed on after its current host's death) and I'm not sure why it would function that way.
3) Saying that if he shapeshifts too much he'll eventually "get stuck" is fine, but it's not much of a trade off for the strength his abilities could grant him. Downsides that are somewhat abstract (we don't know how much "too much" is) and/or far off in the future (we also don't know how long it will be and how much shapeshifting it will take for this to ever catch up with him) don't do well in balancing anything, as they don't tend to affect the person's RP in this current moment and potentially may never crop up in the person's RP at all. It's an okay flavor tidbit for your character, but if your character decides to turn into a tiger and maul someone, it's not a weakness that actually benefits the other player/character in anyway nor one that inhibits your character in that moment. A better downside would perhaps be the transformation being physically painful and taking a notable amount of time, thus leaving him vulnerable and open to attack while shapeshifting.
4) The bit about his father is honestly probably the least unlikely part. Granted, from what was outlined in the OP, we don't have any explanation given for his actions and behavior, which could perhaps raise some eyebrows about why he'd take such dramatic action against his own son for seemingly no reason.
As always, you should of course role-play whatever appeals to you, but if you're looking for lore compliance, I don't think this concept fits.