Put very simply, family matters a lot, but not as much as some other things. It is true that family is an important aspect of marriage and life. But ultimately, you are contemplating marrying an individual. Of course, the influence of the person’s family is a factor. Nonetheless, more important is the person’s own journey and identity.
You may marry “into” a family, but you are not marrying “the” family. People should be assessed on their own merit. Marrying into a warm and supportive family is certainly a plus, and this may be something important to you. Certainly, you may want to avoid a family with a high level of toxicity. For sure, don’t make a shidduch decision based on a family member you don’t get along with. A prospective date should be judged for the most part on their own merit, and not shrunk down to the size of their most unappealing relative.
Having benefit from warm and stable parenting is a major factor in a person’s emotional wellbeing as an adult. However, that is often difficult to find out about. When a person has lived through a high level of family dysfunction – such as addiction, anger, divorce, etc. – this can result in emotional harm, and it is worth understanding how those experiences have affected the person, and whether you are able to handle the effects it may have had.