Is it possible to make a mod that makes a new relationship? Just curious.

You mean a mod that creates a relationship between two sims that didn't have one previously? They'd probably need to know each other in some way first, but I'm certain that's possible in some fashion (and indeed, mods to change relationship levels already exist). Almost any type of mod is possible, though - it just requires the right level of skill and knowledge. If you're interested in making mods, mosey yourself on over to the Create section for info and help on that. If you're just looking for preexisting mods, the Help section has a Where Can I Find sub-section that you can ask for mods to do what you're looking for.

In future though, please use descriptive thread titles.

I dont mean that I was looking for one that says "Serves" as in a butler/maid w/o needing LN

Is it possible? Yes. Does it serve a useful purpose? No. So...not gonna do it. Have fun.

Nah, everything to create a relationship from scratch is already there in the code. It's just a matter of calling it. There's really no point to it, though.

Is it remotely possible that you don't mean relationship, but interaction? Or something like that?

a few mods like MasterController allow you to make a relationship with someone you've never met.

a bit of both

Both relationship and interaction? Now we know you're confused! The two don't have a great deal to do with each other.

Are you looking for the ability to set up a D/s-type relationship between two sims? If so, you'd be best off talking to one of the creators of adult hacks.