This depends largely on an individual's needs. Generally, a good broadband speed for a family of 2-4 is around 100-200 Mbps, which is strong enough to support multiple users online at the same time. Although, if you are working from home, or have kids that are streaming lessons online, you may want to upgrade to a faster speed of over 250 Mbps. You can read all about the best broadband plans for large families here.
*Netflix requires a minimum download speed of 3.0 Mbps to stream an SD quality show, and 25 Mbps to stream Ultra HD films. So if you have more than one person streaming music or TV in HD simultaneously, it may be worthwhile to upgrade to a faster plan.