Think of Abraham Lincoln's family, and Tad or Mary are likely to come to mind. So don't blame yourself if the names Sarah or Thomas Lincoln don't exactly ring a bell. But though they're much less known, both of Lincoln's siblings helped make him the man—and president—he eventually became.

Thomas and Nancy Hanks Lincoln had three children: Sarah, Abraham, and Thomas, also known as Tommy. (Yes, Lincoln was a middle child, a fact that makes his future rise to fame even more noteworthy.) Sarah was born in 1807, two years earlier than Abraham. In 1812 (some accounts say 1813), tragedy struck the Lincolns when their third child, Tommy, died at just three days of age. It is not certain what killed Tommy, but infant mortality was high in that era, especially on the frontier. Lincoln only mentioned Tommy a single time during his public career, but his death must have deeply grieved his family.

Together, brother and sister attended what was known as a "blab" or ABC school, a kind of early primary school common in frontier states like Indiana, where the family moved in 1816. Instead of featuring age-separated classrooms or expensive books or pencils, such schools used a strictly oral curriculum. The "blab" part came from teachers who recited rote lessons to the kids, who in turn blabbed them back. That back-and-forth didn't necessarily provide a great education (and given that the school charged tuition, it probably cost the Lincolns dearly to send them there), but it was enough to instill the basics in both Lincoln kids.

But more grief was on its way for the Lincolns. Just two years after making the rough journey to Little Pigeon Creek and building a cabin there, Abraham Lincoln’s mother, Nancy, contracted "milk sickness" after drinking milk from a cow that had been poisoned by white snakeroot, and died.

Abraham and Sarah were devastated. Though she was only two years older than her brother, Sarah tried to be a mother to Abraham. She also inherited the chores expected of the woman of the house, caring for her brother, father, and a cousin who lived with them.

Just a year later, their father left brother, sister, and 18-year-old cousin at home as he hunted for another wife. When he returned with a new wife, Sarah Bush Johnston, both brother and sister were so dirty and unkempt that she scrubbed them clean. Johnston had three children of her own, and with the help of a new mother and in a house with three stepsiblings, the Lincoln children went back to a life of hard work and sporadic education.

Abraham's sister Sarah was known in her community as gentle, intelligent, and kind. She married in 1826 to Aaron Grigsby and became pregnant. But during her delivery, she died unexpectedly at age 21. Lincoln never forgave the Grigsbys, whom he apparently blamed for not calling the doctor in time to save his sister. A few years later, in response to the fact that the Grigsbys did not invite him to a family wedding, he lashed out in the form of a biting, satirical poem about the event that culminated in a raunchy verse about two men who get married.

Sarah Lincoln Grigsby's grave. Image credit: Stomcl via Wikimedia // Public domain

 
Though Sarah is thought to have affected Abraham deeply with her intelligence and commitment, he seems to have been less impressed by his stepsiblings. In 1851, he wrote his stepbrother John Daniel Johnston a scathing letter denying him a loan of $80 and observing that "I doubt whether since I saw you, you have done a good whole day's work, in any one day."

The letter is tinged with humor amidst the bitterness, like many of Lincoln's missives, but it suggests that his non-Lincoln siblings never stole his heart the way his big sister did. Though Sarah never lived to see his accomplishments, she helped him mature into the person he eventually became—one who met life's challenges with perseverance and, when needed, a bit of sarcastic wit.