I don't mean to criticize anyone but some people only include their only direct family lines and not siblings of ancestors. There are lots of reasons, mostly I would attribute it to a lack of time and let's face it, we all have that problem.
But I recently ran across a stellar example of a reason to include and research the siblings of our ancestors.
I can't quite remember the exact census reference, but that's not all too important. I can't quite remember the names either, but again that's not terribly important.
Ok, we have a woman who we'll call Mary Henley. She was born around 1820.
We have no idea who her parents are. By the 1850 census she was already married to her husband and her marriage record does not give the names of her parents. Her death record doesn't say who her parents are either. She married a man named Frey.
Now we have another woman who lived in the exact same county as Mary. We will call her Anna. She was born about 1822.
Now we do have Anna's death record from about 1902. it says she was born Anna Henley and it gives the names of her parents. John and Susan Henley. Anna later married a man named Meisner.
Now we find that in 1900. Anna (Henley) Meisner, now a widow, is living with a 25 year year old man man named, Mike Frey along with his wife and young children. Some further research reveals that Mike, is Mary's grandson. It also states in the census that Anna is Mike's Great Aunt.
So we know that Anna is Mike's great aunt. And considering that Mike is Mary's grandson, that would mean that Mary and Anna are sisters.
And since we have a death record for Anna, giving the names of her parents. It is reasonable to assume that Mary has the same parents.
So by going beyond the direct family line we are able to find some valuable information or at least a further avenue to study. A person not paying attention to possible siblings of ancestors may miss a vital clue.
More than once, I have found while my direct ancestor does not have a record for parents, a person I can prove is a sibling of theirs does have a record that gives the name of parents.
I thought I would just toss this out there for the benefit of anyone interested.