"Had spelled the name correctly three years ago, but never got a leaf for her to guide me further. Revisited that profile page again last week! Since I knew her brother lived with her in the 1900 Census, I decided to give him a separate profile page of his own (even though I am not really interested in him, since I only deal with direct blood lines). No sooner than that I had done this that I had a “leaf” on his profile page that led me to two ancestry trees that had HIS SISTER (the ancestor of interest) and her ancestry in it..."Do you see the problem here? The researcher was completely ignoring collateral line ancestors. Since they weren't her direct ancestor, she thought they didn't matter. But the minute she added them to her family tree on Ancestry, she got hints that lead her to other family trees for her ancestor.
I often offer to do family trees for friends and co-workers, since I enjoy the challenge. I always ask them to give me information on someone who was alive in 1930 (now 1940!), including any information on their dates, locations, parents, and siblings. I need enough information to distinguish one Lucy Miller, born 1915, wife of William, with daughter Margaret, from another Lucile Miller, born 1916, wife of Bill, with son Edward. If my friend is the descendant of son, Robert, who was born in 1941 and not yet in the census, I'm at a loss. But if I know that they had a daughter named Margaret, I can pick between the two options (and look for further evidence). If I didn't know about Margaret, I wouldn't know which family was the right one.
It's extremely important to research the siblings of your direct ancestors, especially if you're stuck. If you have a "brick wall ancestor" and you haven't tried researching their siblings, you might be overlooking an obvious answer. For example: if my ancestor's death certificate lists her parents as John Smith and Mary Smith, I want to look for the other children of John and Mary to find her maiden name. One of their death certificates might tell me that Mary's maiden name was Quisenberry. Hello! Also, think about an obituary of a sibling that might list the parents, or a society piece in the newspaper that mentions a family visit. Any record that ties your direct ancestor to their parents likely exists for the siblings. If your ancestor's document is faulty, the siblings' document is like a second chance.
You can't stick to your direct blood line relatives if you want your family tree to grow. It's that simple.