A night, click some place outside at click stargaze. If their leaving the house, hungrey, sleepy,Ect. then they will skip the action you tell them to do and do the things they need to do.
There are two or more ways. Obviously, you can let them age naturally. Or you can use the cheat.
Here is how you use the cheat:
1) Go to the neighborhood the sims you want to age live in
2) On...
well, the game is rated T, so that means it's for teenagers and older. so the suggested age is 13 but if your younger and your parents let you that's up to them
go on to your game where ypu want to change their age and click ctrl+shift+c that brings up the cheat bar type in boolProp testingCheatsEnbaled true and press enter and then type in exit to get out...
You can have a baby, a child and then an adult. Its not that good, because you can only have 3 life steps. If you buy the PC version, you can create a family- Baby, toddler, child, teen, yound adult,...