If my parents get a new machine, the first thing I do is uninstall or, at least, delete the icons for Edge, Chrome, etc.. On goes Firefox, uBlock Origin, and a couple other extensions. They don't care what browser they use. They can't even name it. I just try to make sure they use a browser that isn't horribly unsafe.
We should all do this for people we care about. Don't ask them what browser they prefer. Odds are they don't know or care. Don't try to convince them to install Firefox themselves. They won't. Just do it for them. Think of it like picking up a rusty nail that's on their lawn. Sooner or later they're going to step on that thing if you don't.