If you don't then there can be many misunderstandings and fights. Be with them whenever you can and get to know them better. A lot of families now don't get to know each other too well because they're too busy. Plan some family time, like, a movie, or a family game, or even as little as eating dinner together.
Get some friends together--friends who are actually interested in studying, that is--and have everyone bring over their flash cards. Pass them around and quiz each other. If anyone is unclear on a concept, take turns explaining them to each other. Better yet, turn your study session into a game like Trivial Pursuit.
The most effective way to retain information is to "tie" it to existing information that's already lodged in your mind.
You don't have to memorize them, but whenever there is an important concept in a particular field, there is usually a special term to refer to it. Learn these terms, and be able to use them easily, and you will have gone a long way towards mastering the subject itself. (Besides, teachers frequently draw from these lists as a quick and easy way to make up test questions!)
Traditionally, this is done with index cards, but you can also download computer programs that cut down on space and the cost of index cards. You can also just use a regular piece of paper folded (vertically) in half. Put the questions on the side you can see when the paper is folded; unfold it to see the answers inside. Keep quizzing yourself until you get all the answers right reliably. Remember: "Repetition is the mother of skill.