Regardless of what system you use, your family members will always only have to connect to the shared folders. If they just want to backup and browse files, they won't have to touch a terminal, ever. That's the whole point of NAS.

So it's really a matter of your budget and how much time you're willing to spend setting it up. For instance, a 5-bay hard drive enclosure and an old 7th gen i3 NUC will do most of what a Synology DS423+ will do and will save youa about US $250. But the synology will take you 2 hours to setup and a few hours of tinkering if you wish whereas the NUC will take many hours of tinkering and setup, depending on your skill level. You'll also end up with a less polished interface on the NUC setup.

So if you're the kind of person who loves playing around with custom built system, pickup whatever you like and set it up to your preference. If you just want to get something and have it work, go for Synology.

Oh, and also, Synology shares a lot of data with Synology servers. Mostly it's not a concern, but if you worry about that kind of thing, you might want to know beforehand.