Your family is the most important thing in your life. You live to see your loved ones happy and comfortable, and you do whatever it takes to make that happen -- sometimes at the expense of your own comfort. In the end, though, you wouldn't have it any other way. You likely want a big, loving family of your own someday, or at the very least it's important to you that you stay in touch with the family you have now.
In the game, Family Sims typically want to have children, see that their children grow up well and go to college. They also often want to appreciate or talk to their families. They tend to be the most altruistic sims in the game, as many of their wants revolve around the success of others.