So basically we use the parents & kids from each generation and pick the funnest time periods.

Easy!
Liz, Rhia, Tristan, Kisla etc - 1930s, Great Depression, jazz music, prohibition, WWI & II
The oldest kids (Devon - Nare, Mia, Jason) - 1940s, WW2, Cold war
The middle kids (Quads, Ella - Carmen, Chris) - 1950s, greasers v. squares
The youngest kids (Twins - Kio, Maria & Tilla, Amy & Ashley) - 1960s, drugs, hippies, civil rights, Vietnam War
Second generation (Sol, Aunrae, Brogan, Kael, Em, Cheyna) - 1970s, glam rock scene, more hippies, disco
Second generation (Brandon, Chase, AJ, Jordan, etc) - 1980s, harder rock scene, Sunset Blvd, etc
Third Generation (Lance, Scout, etc) - 1990s, grunge scene, Desert Storm
well, watcha think?