Making family members infertile

[CIaagent11]

I want my family members not to have kids, and only adopt.
Can I do that by adding

Effect Fertility -5

to the LoyaltyStarter in BI:

Trait LoyaltyStarter
Characters family
Hidden

Level Loyalty_Starting_Value
Description Loyalty_Starting_Value_desc
EffectsDescription Loyalty_Starting_Value_effects_desc
Threshold 1

Effect Loyalty 4

My question is only, if all factions then will get the infertility, or only the romans.
I want it only to work for the romans. Other factions family members don't have the loyalty counter,
but the trait does not exclude the other factions.

Thanks for any help.

Edit:
Making it not Hidden reveals that other factions also have it.
Any idea how to get family members to either not marry or not to have kids?

[Squid]

First if you want the romans to have it only, make a new trait that only romans get. Second, if you search this has been discussed at least 2 times in the last couple of months, there is no way to stop marriages form happening.