Unique traits?

[BozosLiveHere]

To make the ancillary unique all you have to do is add the Unique line to it, like you would add Hidden to a trait, like this:

Ancillary BozosLiveHere
    Image BozosLiveHere.tga
    Unique
    Description BozosLiveHere_desc
    EffectsDescription BozosLiveHere_effects_desc

As the others have already said, there's no straightforward way to get a unique trait. In the case you mentioned maybe you could do something like this:

Trait Fatherhood
    Characters family
    Hidden

    Level Firstborn
        Description Firstborn_desc
        EffectsDescription Firstborn_effects_desc
        Threshold  1

    Level FirstbornBecomesAdult
        Description Firstborn_becomes_adult_desc
        EffectsDescription Firstborn_becomes_adult_effects_desc
        Threshold  32 ;assuming you're using 2 turns per year

    Level FirstbornAlreadyAdult
        Description Firstborn_already_adult_desc
        EffectsDescription Firstborn_already_adult_effects_desc
        Threshold  33

;----------------------------------------
Trait Firstborn
    Characters family

    Level OnlySon
        Description Only_Son_desc
        EffectsDescription Only_Son_effects_desc
        Threshold  1

In the trigger section you'd have:

Trigger Becomes_Dad_For_The_First_Time
WhenToTest CharacterBecomesAFather

Condition Trait Fatherhood < 1

Affects Fatherhood  1  Chance 100

;--------------------------------------
Trigger Firstborn_is_getting_older
WhenToTest CharacterTurnStart

Condition Trait Fatherhood > 0
        and Trait Fatherhood < 3

Affects Fatherhood  1  Chance  100

;--------------------------------------
Trigger Firstborn_gets_his_trait
WhenToTest CharacterComesOfAge

Condition FatherTrait Fatherhood = 2

Affects Firstborn  1  Chance  100

I could not get the FactionwideAncillaryExists & WorldwideAncillaryExists conditions to work in the traits files in BI 1.6.

Really? I thought I'd seen WorldWideAncillaryExists in the vanilla edct. Gah! There goes my idea for using scripts to affect trait acquisition.