Make a civ like certain other civs more?

[Ankorafeonix]

I want to add a feature to the game where certain civs have a tendency to be friendly with other certain civs. For example, I want Russia to be quite friendly with my custom Belarussian civ for a scenario, but they always end up heckling over territory. I don't want to make them a single team however.

I can't see any way to adapt the GlobalDiplomacy Defines to this purpose, so I'm assuming I'll have to create some kind of lua script that creates positive opinions between these "friendly" civs on game start. Is that right? The only problem I see with that, is that opinion decays over time, and eventually the bonus won't be noticeable any more.

Is there a way to create this kind of friendliness between civs that never decays or dies off? Even if they do somehow get angry and fight with each other. Thanks!