Let's take for our example the hypothetically average student. He or she belongs to an "average" family of mom, dad, 2.5 kids, and a dog/cat. It's probable they may have a step-parent, perhaps some half- or step-siblings. Let's then assume the biological and non-biological mom and dad have 3.5 siblings each. Though marriage isn't for everyone, perhaps more than half of those people themselves have a spouse or more with 2.5 kids of their own. Though your student probably doesn't know them so well, their grandparents likely also had siblings, probably at least 4.5 each.
Let's step back and visualize this in another way.
Our student has his brother and a dog or cat. This student also has a bunch of cousins, aunts, uncles, and at least four grandparents. Some amount of these people have sadly already passed away. Perhaps some are long dead, even some of them may be in prison. Once you add in the extended family of the grandparents, your student has some unknown mass of second cousins.
More likely, your average student is aware mostly of their aunts, uncles, and first cousins. Well, some of their first cousins, though not necessarily of all their first-cousins once-removed. It is unlikely that your student is on a first name basis with all of the cousins of their parents. Any, most, or all of this vast array of people could be living in one town, fifty towns; one country or five countries; one language/culture or two or even three different languages/cultures. This country is supposedly a melting pot, after all.
Perhaps this is the typical American family - though of course, there are those who are not only only-children, but the single child of only-children, having no aunts, uncles, or cousins. However, that is pretty unlikely, and eventually everyone has cousins, be they second, third, or fourth cousins.
Quick Note on Cousins: In English we have a limited vocabulary compared to other languages for distinguishing relatives. Even the vocabulary we do have is under-used and often misunderstood. A "first cousin once removed" to you would be how you refer to the children of your first cousins and also how you would refer to first cousins of your parents. An easy example is to imagine that your favorite cousin Jim has a child. That child, let's call him Teddy, is Jim's son. Jim is your first cousin, but little Teddy is your first cousin once removed. Similarly, if your dad is really close with his cousin Jill, she is also your first cousin, once removed. If you want to be more specific, you would describe her as your first cousin, once removed, on your father's side. This still doesn't explain to your listener which type she is (child of cousin or cousin of parent), but the context usually makes this clear. Again, there are other languages that handle this situation with fewer words and less confusion.
In short, family relations are just about the most confusing thing to talk about and explain, yet the vast majority of humanity has them in abundance.
My thought is to use this to our advantage in teaching history.
Your student with their typical family -- they are sitting in your history class in High School or at college. Ask this student to imagine the people in their family - even better, have them draw a "family tree" as best they can, including as many relations as they can handle, including first cousins, even once or twice removed cousins where they are known. Get aunts and uncles in there, step-parents and half-siblings, Uncle Thomas who was really a foundling, plus grandparents, great-grandparents, whatever they can handle. Some students will have tiny family trees and others might have gigantic ones. For a learning experience, perhaps have them make one family tree in class and then have them turn in a "complete" or "official" family tree at the end of the semester with birth and death dates for as many people as they can manage. Ask them to be as clinical as possible in both cases, understanding that death, sickness, and time are working on all of our family trees.
Now that your student has this gigantic cast of characters, have him or her attempt to create some general narrative of their family history, focusing on their own "pedigree." This is the super simple family tree, from parent to child. Build from that story using stories they have heard about their parents' childhood. Perhaps they can write some notes about how mom and dad met, their courtship and marriage(s), various children, occupations, economic-social class, religious affiliations and hobbies, focuses and personal beliefs. This should be fairly easy and also allow the student to explain some of their own feelings and personal beliefs, positive and negative, allowing that everyone's family has the capacity to cripple and amaze, to disgust and inspire.
At this point, have them pick a cousin of the same generation they know pretty well and explain how their view of the family is probably different. Then put themselves in an uncle's shoes, or that of their cousin, once removed on their father's side. It becomes more difficult as they have to rely more and more on hearsay and publicly available documents. Even more so, they will notice that as they consider their relatives with their varying military, occupational, and religious backgrounds, their own likely values and beliefs may change in both expected and unexpected ways.
In a large family, one member may best explain their relatives according to their duties and a sense of honor lived in service to one's country or community. For another member, the socioeconomic status and ability to rise past or maintain the station of the parent is more important. For another, the trials and tribulations of health and family trouble are best explained through devotion to certain values, beliefs, and religious affiliations.
History is much the same way - some historians are most interested in Military History, others in Economic History, still others in Anthropological or Sociological discussions of rituals and practices and their explicit and implicit meanings. Not only that, but these categories are leaky and fungible, so that Uncle Frank sees the world both through military service and devotion to various organizations, though he may not articulate such so clearly. In fact, when he was younger, he focused more on technology and a sense of progress, while those considerations are not as meaningful to him now.
Family relations are a rich source of didactic models and history as the story we tell ourselves about the world around us can learn much. It also allows the student-historian to practice self-reflection and to see the difficulty of "walking in another's shoes." If you can attempt to see where and how you fail to visualize the inside of your mother's head, you will be all the better prepared to imagine historical figures of another gender, time, or culture than your own.