What happened to Abraham Lincoln's 3 sons?

Lincoln actually had four sons:

• Robert Todd Lincoln - Lawyer, Politician, and only on of Lincoln's four sons to live to adulthood (Died at 82)
• Edward Baker "Eddie" Lincoln - Died at the age of three
• William Wallace "Willie" Lincoln - Died at the age of eleven
• Thomas "Tad" Lincoln - Known to be impulsive and unrestrained, did not attend school, and outlived his father but died at the age of 18