Specifically, that logic is in the "conceive" function which you can search for if you do the full assemblies search, which normally returns if FetusCount > 0, which basically means it does nothing if there's more than zero fetuses. For testing purposes, I just changed the FetusCount to check for > 2, which means it can add more fetuses if there is not already more than 2 similar to how the rabbits worked in MBM; it's not an elegant way of doing it, but it was the simplest way I could see to override the check. You can see when it adds another fetus as it also resets the pregnancy's development as that's part of the same function.
I've also included a zip with the replacement .dll that has the above change (it also includes AutoBio's sacrifice mod that heals the door as I had that installed when I was tinkering). Just replace the assembly .dll in the "managed" folder
Multiples are an unfinished feature in the assembly scripts (not the notepad accessible ones, the .dll ones). They kinda work if you remove some of the checks to force them to occur but they are missing some animations.
The colour scripts are only accessible in the character scripts in the assets folder in the earlier versions. In the latest version, they have been folded into the main game logic scripts for some reason. Still technically accessible, but far trickier as it requires specialised programs to decompile.
And speaking of the colour scripts, I do want to sit down and try to figure out how they work as it seems like they are actually fairly complex. as they keep track of half the family tree for some reason.
