Welcome to WikiTree Lori! If you have living family that are links to ancestors, such as: your parents are living and you need to add them in order to add your grandparents, etc. , then yes, add them. They will be completely private unless they join WikiTree. I only add living people in order to connect to a line that I want to add. I have added both my daughters and their husbands so that I could add the husband's family lines and do the research for the grandchildren. It is all personal preference or need.
I hope this helps and I am sure others will post their ideas on this.