Appreciate the suggestion but I don’t think that actually fixes it, wanted to explain why in case it helps anyone else running into the same thing.
Custom Relationship Labels are just cosmetic text. It’s the same feature that lets you rename “Romantic Partner” to something custom. It’s not tied to the actual family tree, the Distant Relative bit, or Dynasty tracking at all. So you can type “Second Cousin” on two sims and it’ll show up that way in the relationship panel, but nothing about how the game actually understands them as related changes anywhere else.
It also has nothing to do with romance eligibility. Who your sims can actually pursue romantically is controlled by the family tree checks (the new ancestor block plus the old first cousin restriction). A cosmetic label lives completely outside that system so it can’t be granting or blocking anything there either.
And honestly it just doesn’t scale. There’s no way to bulk apply it, you’d have to go through every single pair manually through the pie menu. In a save with 200+ sims that’s not really a fix, that’s hours of busywork, and you’d have to keep doing it forever as new sims get born into the tree.
What would actually help here is a real settings option for this. Right now it’s basically nothing, we could have either full guardrails where any relatedness at all blocks romance, or no guardrails if you turn off the restriction entirely. Neither one may really works for a lot of others story progression. Some of us want that in between option, where romance is only blocked up to a certain point of relatedness, so first cousins and closer stay off limits but second cousins and beyond are fair game. That’s honestly how a lot of players (and a lot of real world cultures and history, especially with royalty) actually approach it, so having a slider or a toggle for where that line sits would solve both the labeling problem and the eligibility problem at once, instead of needing mods to patch around it.