Dojutsus are highly considered KG, but it doesn't necessarily mean that every dojutsu traces back its origin to Kaguya's bloodline.
We have the Three Great Dojutsus and it makes sense for them to be revered as "Three" and "Great." They all came from one bloodline.
Now, i'm not closing doors to Ketsuryugan or whatever. It can be an evolved eye, a dojutsu of her own with no apparent link to the Ootsutsuki Clan. It can also be a branch off somewhere along the progeny.
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All the doujutsu wielders are of Otsutsuki linage though!... KKG can be used among other clans but not Doujutsu KKG..
There are no KKG KKT doujutsu users who are not of Otsutsuki lineage in the series so this Ketsurygan has to be of Indra bloodline..
(But there's no mention of kids as far as his bloodline goes just descendants which also doesn't make since if there's no kids)
Somethings missing as usual!..
OT:
Reviewing Logic made a good point about some1 from the Uchiha clan went rogue an ingaged in another clan to produce the Ketsurygan..
(It's still leaves the question of where did this doujutsu come from if Indra has no kids, an no kids means no descendants)