First find a man/woman then do a pick up line FIRST to get them under your thumb. When you have been romantic for a while and when "purpose going steady" shows up click it and if they say yes then the next time you socialize or flirt with them it will say Boyfriend/Girlfriend. Then you have to be romantic with them again and it should say "purpose marriage" or something like that and when you click that if they say yes; then it will say Fiance. So if you want a more romantic wedding you can click "have private wedding" or you can throw a wedding party! This is a process. This is a kinda weird statement but you can be gay or a lesbian and marry or date your own gender! WARNING: I've don't have the Sims 2 so I don't know if it's the same but I do have Sims 3 Master Suite (PC) and the Sims 3 Pets on XBOX 360.