Issue means the various biological descendants that a person may have. For example, a person may have children, grandchildren, great grandchildren, nieces, nephews, etc. There is a wide variety of different types of descendants that a person may have as a part of their issue. A person's issue can be important in the case of wills or other areas of family law.
An issue is also the factual reasons involved in a lawsuit.
Issue basically just means the descendants of a person who are biologically linked. A person may have many friends and acquaintances, but this is different from being biologically linked. Biological connection must come from reproduction. A person must share genetic material with the person in order for them to be a part of the person's issue. DNA testing is currently available to help determine whether or not people are biologically related. These tests are very accurate.
An issue is also the reason why a lawsuit is filed. A lawsuit can have more than one issue. For instance, if there is a civil lawsuit because of an auto accident, there can be several issues including negligence, failure to devote full time and attention to the rode, and claims of personal injury.