How we are affected by our family background varies. But most of us are shaped by our family and upbringing. Some people become very much like their parents. Some make conscience decisions to be different -- whether or not they're able to is another story. Having a basic overview of your mate's family background can give you a window to interpret who he is.
Drug or Alcohol Use
Many people are able to conceal drug and alcohol abuse for a long time -- even from people who are close to them. You should be aware if there are signs of drug and alcohol abuse or if there are any indications of possible substance abuse. Observe whether drugs and alcohol are ever used in front of you. You should know how much and how often and what the visible effects are. Be aware of potentially indirect effects as well, like mood swings, unpredictable behavior or fatigue.
Getting Over Past Relationships
It can take a year or more to emotionally process a breakup and be ready to try a new relationship. Some people simply do not move beyond the emotional injuries of old relationships and remain stuck on them indefinitely. It's not necessarily a bad thing to learn about your mate's past relationships; it may help you understand her. But, once you've learned about her, beware if she starts obsessing about past relationships. It is a good indication that a person is not emotionally equipped to move forward into a new relationship.
Knowing What Your Mate Wants
Just as you are well served by knowing what you want from your life, you should understand the basics of what your mate wants from his life. One way to do this is to simply ask, "What do you imagine your life like in a year, two years, five years or ten?" Pay close attention to the things that are mentioned. You don't have to have identical lists. But your expectations and priorities should be known to one another. If he mentions kids and kids aren't on your list -- don't gloss over it. Be direct. Ask questions. The answers don't need to be deal-breakers. But if they happen to be, you're both probably better served to learn it after four months instead of four years.