What happened to lincolns other sons edward willie and tad?

Abraham Lincoln had four sons, but only Robert survived into adulthood. Edward, often called "Eddie," died of typhoid fever in 1850 at the age of four. Willie died in 1862, also from typhoid fever, which deeply affected Lincoln and his wife, Mary. Their youngest son, Tad, survived his father's presidency but died of pneumonia in 1871 at the age of 18.