Dorothy Mengsk was the daughter of Angus Mengsk and Katherine Mengsk, and younger sister of Arcturus Mengsk. She was very close to her brother and father, her innocent personality touching both of them and often allowing her to bend them to her will. She also enjoyed sugary sweets.
Physically, Dorothy had long black hair, her mother's high cheekbones and her father's brow.
Dorothy was named "Little Dot" as a baby, a period in which she was rarely seen without her stuffed toy pony Pontius. She was able to read by the age of four, though her speech was not fully developed yet, as she was often mispronuncing her brother Arcturus' name.
During the formative stages of the Rebellion of Korhal, neurally resocialized Confederate marines, disguised as a corporate death squad, broke into and rampaged through the Mengsk summer residence. Dorothy and Juliana Pasteur were present in the residence during the attack but both slept through it unharmed. Juliana had read Dorothy a bedtime story prior to the raid.
Dorothy was incensed when Arcturus left to join the Confederate Marine Corps without saying good-bye. As a result she refused to allow her brother to call her "Little Dot". However, she constantly watched the news, despite her parents' disapproval, and wondered whether Arcturus was still alive. Reaching the age of six, she became the "matriarch" of her kindergarten class. When Arcturus returned two years after leaving Dorothy initially refused to speak to him. The two reconciled soon afterwards, especially when her brother returned with a present, and she allowed him to call her by her nickname again. Unfortunately, Arcturus once again left the family on bad terms.
Despite her brother's sudden departure, Dorothy still kept in touch with him via vidphone over the next four years. By the time she was eleven, she had reached the stage where she was interested in parties and members of the opposite sex and by the age of thirteen, had attracted a great deal of attention from them in return. Various suitors from wealthy families began to court her, only for Angus to send them packing, telling them to come back when she turned 21. Dorothy's enjoyment was restrained in that she was not allowed to leave the house without soldiers escorting her, as per the deteriorating situation on Korhal.
Regardless, she was alongside her parents during the declaration of Korhal's independence in 2489. Shortly afterward, Dorothy, her father, and her mother were killed by Confederate ghosts. This inspired Arcturus to take up leadership of the Rebellion of Korhal.