Families can be formed by blood/birth, marriage, adoption or less formally by developing a relationship.
Some of the variations that families can have are "nuclear" that is just a single parent or a couple and their children, "extended" over multiple generations with in-laws, siblings or "blended" two or more sets of children in one household after their parents marry or "connect" with other parents (half-siblings, step-children, etc.)
Some family relationships are legally recognized: parent-child, marriage, adoption.
Sometimes a residence is designed to support nearby or extended family living. For instance, some houses are duplex -- two adjoined homes -- or a secondary suite, also known by names like "mother-in-law" apartment. This can provide some privacy and independence in conjunction with family support.