When I started working on my genealogy, I knew nothing but my grandparents names, I didn't know them, The very first thing I did was to read my grandmothers obituary in the newspaper. It was not a lot of help but my grandfathers was much more useful.
When you don't know the siblings of your ancestors, reading an obituary is one way to get their names. Often obituaries list the siblings, both those who are living and those who are deceased. It also givies the married names of the females which is a big help.
Obituaries of course, are not a primary source. There is no telling who gave the information to the newspaper, it might have been a child or a bereaved spouse. Some will have incomplete information and some may be downright wrong but they are fascinating to read, especially in the Victorian and Edwardian eras. They are very flowery and you will learn a lot about the funeral service, flowers and what church they attended if any.
You will also see where they were buried.
I began at the local library and spent many fruitful hours pouring over old newspaper films. It is hard work but it is also very rewarding.