If two people are watching HQ videos (netflix, youtube, etc), that's easily 8-10mbps *minimum*. Figure the other two are listening to music and playing online games and maybe you have a guest who is using skype or something... bandwidth just doesn't go very far in today's world, unless you're living like it's still the late 90s as far as your entertainment consumption and communication.
Yeah, you're a dammed primitive if you stream videos in less than 4K!
You've thrown-out all your DVDs by now, haven't you? They're only 480p, if you're lucky, you cave man, you...
Meanwhile, 16:9 480p looks pretty good on my 40" HDTV, and Hulu streams it in DVD quality at 750Kbps (works at 500Kbps, too, if you don't mind some artifacts)... At that rate, 5 people could be streaming different videos *simultaneously* on your "late 90s" internet connection, with headroom for other stuff at the same time.
And personally, that sounds like a nightmare of a family life to me... This may not be the 50s, but everyone alone in their rooms, watching their own HDTVs, all-day, every-day (has to be *simultaneous*, remember?), nobody watching things together, nobody out doing any other activities, etc.