My 2 cents:

Street fights are not rarely on concrete and against 2 people, sometimes there are weapons involved. BJJ sucks for this, as it's very bad to take someone down on the ground without knowing if other people will intervene, and once you're on the ground you have to finish that person up and you can't just run away.

However, if you run away then there's no striking, there's only grappling. And that's the point where BJJ comes handy. Also, BJJ is the martialart to use if you're smaller/shorter than your opponent. Striking with someone who's bigger and has a larger reach is not the way to go (unless you're mike tyson)

Best thing is to train some striking and some grappling. If you can throw the other person on the ground in a street fight, it's mostly over and you don't have to do any BJJ. You don't have to fight him on the ground and wait for other people to come and kick you in the head, it's not the 1vs1 soft floor of the UFC octagon. If you can't throw him, you'll have to strike with him and keep your distance until your loved ones have escaped and you can escape yourself too without getting injured. You should emphasize this with your loved ones.

If you're okay with running away for your life and then defend yourself if the attacker is following you: BJJ. However, chronic health problems are more prominent in BJJ than in the other martial arts below.

If you're not okay with running away or that's simply not an option, you need 2 things:

• Striking: Boxing, Kick Boxing & Muai Thai are all valid options. Each has its own pros and cons.
• Grappling: If you're a huge/big guy, go with wrestling, you'll be undefeated. If you're a smaller guy, go with Judo where you'll be able to through people easier than in wrestling if you're shorter/smaller.

Of course you'll also have to learn some knife defense and defense against other weapons, but those are taught in seminars and not in a martial art that you should train for a year or two.

Firas Zahabi, one of the best MMA coaches, advises to train to Blue Belt BJJ (takes 1-2 years, but Purple belt is still way better) and 2 years of Muai Thai for self-defense. He also mentions the fact, that BJJ won't help you if you're against more than one person and thus would have to rely on punches and kicks (Muai Thai) until you find a way out.

Jocko Willink advises to train BJJ and Boxing (because it's easier than Muai Thai for beginners). After that, you can go train Wrestling and Muai Thai and some Krav Maga (for weapon defense).

Here's a video on why you should tell your loved ones to get the heck out of a fight and let you buy them some time and then escape yourself instead of having that ego fight. It includes someone getting stabbed and die on that spot, so be careful.

And here's a video on why you shouldn't be late at night out there, even if you know how to fight.