Explore Family Patterns and History
Take time to explore family patterns and history before you marry. For example, it does matter if his father is an alcoholic. This means he grew up with specific interactional patterns that will need to be addressed because they will impact your relationship. It does matter if you have significant religious differences. It does matter if she does not get along with her mother. It does matter how he deals with conflict based on his original family, etc. Identifying family patterns and working on blending them makes a big difference.