Okay, thanks! Thank you for the welcome too!
As to what mods are---I am terrible at definitions so I will borrow this definition from Twallan---
A mod is defined as being any package that contains scripting, either in the form of a Core-Mod, or as a Scripting Mod, that was not created by EA.
[ Note that EA Premium content contains new scripting (hence why it is considered "premium")
Strictly speaking, these are essentially mods created by EA, though for clarity purposes, no one bothers including them under this term.]
He has a bunch of terms defined on his site.
Basically they change your gameplay in some way---whether it fixes a bug, or adds new interactions in, or??? I played Vanilla (without mods) for years until the release of Late Night and I could not control the vampire/celebrity explosion. It was game breaking for me.
I was spending all of my time curing vampires and I wasn't having fun anymore. People on the main forum kept mentioning this Twallan guy and that his mod StoryProgression could keep them from spawning---since I wasn't going to play anymore the way it was---I took the plunge!
Anyway---back to topic! Sorry! MasterController lets you do a lot of things. It is a *passive* mod in that there is nothing automated in it, it is all user directed. To repair the family links you actually will need MasterController the base mod and the Cheats Module. When you install it it adds in a menu that you can access by clicking on the City Hall, any computer, even the Sim itself---a NRaas MasterController menu. Then it's simply a matter of navigating to the Advanced/Family interaction and you can add/remove a sibling/parent/child to any sim in your town, using any sim in your town. I hope that wasn't confusing!
As to the negative---it is possible to download a *bad* mod, which can cause havoc in your game, possibly even ruining your saved game. The easiest way to avoid that, is to do lots of research and ask around. People who use mods are quite vocal on the ones they like! (See my post above! lol) Twallan is always a great choice!
The only other thing you have to be careful about is your patch level, you have to use a mod that corresponds to your patch level, or they simply don't work right.
Sorry for the long post. Hope that helped you out some.