Does MCCC Make Multiples More Likely?

I don't think so exactly. I think that's the game itself (I notice a lot of people who don't use mods still get lots of multiples), but you can actually set the limit in MC pregnancy. Also of you want only child for a specific sim, click on them to determine how many babies they'll have.

There is a Risky Woohoo option but it only activates unless the player presses it and sets a percentage for it.