Often, as part of their seasonal rounds, many individual bands may come together into a larger group. They recognize all of these members of the larger group as being the same people. They share the same language and culture. At this gathering time they often have celebrations and often exchange marriage partners. Thus these individual bands are related to each other as well.
Bands are in flux.
Individuals sometimes move into another bands and always maintain relationships with other bands. In times of food shortages these relationships with other bands can mean survival rather than starvation. Although in reality residency patterns are more fluid. And it may be possible in a normally patrilocal culture for a couple to reside with the wife's family. Because hunters and gatherers have a widely-varied diet composed of plant foods and animal foods, their nutritional status is often superior to that of agriculturalists.