If you type in "testingCheatsEnabled true" into the cheat window, you can then hold down shift and click on a Sim. It will give you the option of triggering the sim to age. you can keep doing that until they die.
It died of disease
they can die if they don't get all of there needs or wants or food
One of your sims has to die. After the sim dies, the Grim Reaper shows up and takes the sim with him. He leaves behind a tombstone or urn (depending on how the sim died). If you don't delete the tombstone or urn, then once in a while the sim's ghost will wander around the lot. It will only be on the lot where the sim died. You can't control the ghost, and it will scare people.
Your Sims cannot have a miscarriage. Although, they can die while pregnant.
Alexander Cameron Sim was born on August 28, 1840.
Alexander Gordon Cameron died in 1944.
Alexander Cameron - businessman - died in 1893.
Alexander Cameron Hunt died in 1894.
William Alexander Sim died in 1928.
Alexander Cameron Rutherford died on 1941-06-11.
Robert Alexander Cameron died on 1894-03-15.
Duncan Alexander Cameron died on 1888-06-08.
John Alexander Buchanan was born on March 4, 1887.
John Charles Alexander Cameron died on 1976-03-24.
Alexander Cameron - businessman - was born in 1827.
Alexander Cameron Hunt was born in 1825.