Don't neglect siblings, aunts and uncles, cousins, even "in-laws", they are all part of the puzzle. I am especially happy when I find a photo of a member of my family, and remember that people have been sharing photos with their distant relations, and in-laws, for over 100 years. That photo you want may show up in the possession of a distant cousin. It has happened for me several times and it is pure joy.
If you are descended from royalty, chances are that would have already known that. You probably aren't, most of us are common folk. And that family story about "the guy who fought with George Washington" may or may not be true. That's no place to start. Start with your own pedigree. You'll get there.