No marriage mechanic exists. The GameCube port of The Sims 2 (2005) is a stripped-down "Story Mode" with linear objectives. Freeplay is a sandbox but lacks:
Propose/Go Steady interactions.
Wedding arch / ceremony objects.
Family tree / generational gameplay.
What You Can Do
Max relationship (100) → Sims may autonomously "Woohoo" but no pregnancy.
Use "Move In" interaction to share a lot.
Pretend—roleplay a wedding with party items (cake, dance floor).
Platforms With Full Marriage
PC/Mac (base game), PS2, Xbox, DS (limited), and all later Sims titles.