Your mum is sort of unofficial Order, isn't she? So there's that. And all the people who work for Bill. Besides Archer, I mean.

There's just a pile of people at Moddey Dhoo, and it's frightfully hard to tell who is what unless Mrs Longbottom says something like 'So and so brewed a potion' or 'such and such got her wand today.' There's that Stephen person, and Arabella somebody, who's the lady in charge, I think? They're magical, and there's a few other people they talk about a lot only it's not clear at all who has wands and who doesn't. Except for that one mad-sounding one who comes up with weapons. Fu Lee. I'm sure he's a Muggle.

Can Muggles brew potions?

I don't think so.