The Sims Castaway Stories on Wii deliberately omits romantic interactions, "WooHoo," and pregnancy mechanics. This wasn't an oversight—EA Maxis made a conscious design choice to keep the experience accessible to younger players.
If you want the full life simulation with romance, families, and generational gameplay, the PC/Mac versions of The Sims 2 or The Sims 3 (with appropriate expansions) are the appropriate platforms.