On the drama series The O.C., Summer Roberts (Rachel Bilson) and Seth Cohen’s (Adam Brody) relationship spans all four seasons and features highs, lows, and many memorable moments. Since Summer is cheerful, wealthy, and popular, and Seth is a self-proclaimed nerd who enjoys video games and spending time with his parents, neither character expects the romance to happen. Ryan Atwood’s (Ben McKenzie) arrival in Newport Beach is the catalyst for Seth and Summer sharing their feelings and becoming each other’s soulmates.
https://screenrant.com/oc-seth-summer-relationship-timeline/