Madison met Steward first, she got injured when it snowed and she let him carry her towards her car. She had a relationship with him but he’s too busy that he asked her to look for another boyfriend, just someone that could take care of her and satisfy her (sex) cravings while he’s working. That guy would be Paul, a surfer. She met him in a carnival where they had a ride, kissed and had sex.
Madison is already in a relationship with Paul and Stewart, and both guys are okay with sharing her, just to make her happy. While surfing, she had an accident which caused Paul and Stewart to meet, which turned out that they were brothers. Stewart and Paul drifted when their younger sister Jennifer died because Paul allowed her to go somewhere.
Maddison almost died on that accident but was still saved. That accident fixed things. Paul and Steward forgave each other, and she had the chance to choose which lover she’ll stay with.
End: It was Paul and Madd. Stewart found someone else.