Teen Sims in The Sims 2 are taller than children, but shorter than adults and young adults. The teen life stage lasts for 15 days although Teens can be aged up.
While Create-a-Sim doesn't allow for households without adult Sims to be created, you can still make teen Sims live alone or with other young Sims if you choose. This wikiHow will teach you how to make teen Sims live alone in The Sims 2. Teens can care for Child Sims or younger.
By default, The Sims 2 doesn't allow for teenage pregnancy; however, there are third-party hacks available to enable it, and it's also possible to.