Seth and Claire first met when they were both in Sophomore year at Sint Joseph's Boarding School. When Claire walked out of her room she bumped into him. Both of them immediately knew what the other person was and although Claire was scared, she decided to give him a chance as she felt like he didn't meant any harm to her or her sister. They happened to be in the same class and despite them being natural enemies they became friends rather quickly as Claire kept being interested in him and asking questions. Seth wanted to keep his distance a little, but he didn't seem to stay away from the blond curly haired girl. They started to hang out more and more to disapproval of Payton. When Seth started noticing that Claire might be in love with him he started to think differently of her to. He always pushed away the feeling of being in love with her, because that would be very dangerous for both of them. When he finally let his love in, after he found a picture Claire drew of him, the new it-couple was born. He took her up to the waterfalls, where they shared their first kiss.
During their highschool years they were a constant couple. When Claire went away to go clean up after one of the party's at the high school she got kidnapped by the brother of Jason. When Seth found out he was determined to find her and to save her. With the help of his family and her sister he was able to get her out of their, promising himself that he would never ever let her out of his sight again. Seth had to leave for a little while in Junior year though, because he started transitioning. Making his love for Claire eternal. Despite some people wanting to break them up (Justin in the beginning and Douglas during their whole relationship) they always stayed together. During his absence Seth made sure that Claire had something on her mind, so he signed her up to become Junior Prom Queen. They were known as one of the favourite couples from SJBS and that helped in both their popularity. Seth as the star of the track team and Claire in general.
In the last year of highschool they both lived in the Silverstone house.
After Claire's summer internship it is revealed that she got offered a job to work at vogue, which would make her relocte to New York permanently. When Claire tells Alyssa, Alyssa answers with the question if she wants to break up with Seth. Claire is confused, which is when Alyssa tells her that Seth can't enter Miller teritory without having a target on his back. Claire then suddenly realises why Seth never could visit her during her internship, and she goes to talk to him about it. When Seth admits that, Claire decides to pass on the job offer and she focusses on her third year of school again. (sep 2012)
Claire launches her newest collection, and at the celebration party at the Dawson house Alyssa notices something strange about Claire. Concerned that Claire might be ill, she talks to Elisabeth. When Claire gets really ill, she collapses at the Dawson house. Elisabeth takes Claire to the medical room. There, separated from all the other noise, a particular sound hits Seth's ears. Another heartbeat. When Elisabeth runs a test, it is revealed that Claire is 10 weeks pregnant.
Seth and Claire put the conception date around mid-october, but Elisabeth is still a bit confused as to Claire's symptoms and blood levels. The next few weeks, Claire starts showing rapidly, and she considers dropping out of school because the stress affects the baby. This decision is fortified when on the next ultrasound Elisabeth reveals Claire is pregnant with two babies.
When Liam shows up at Claire's birthday party Seth is one of the people that is willing to hear Liam out. This creates an argument between Claire and Seth, but ultimatly Seth agrees that Liam brings danger into their lives, and that they need to protect their daughters from him. Things go the bad way when Seth gets too protective. He takes Claire with him to Chicago because he thinks Elisabeth and the others are going to steal his baby. Eventually, he bites Claire and toxicates her and the babies. However, the babies are able to fight the toxic off. James then finds out Seth has been shot with a special hunter's bullets. When they remove the bullet, Seth returns to his old self again. Claire and Seth decide to name them Amanda and Alexis. Amanda refers to Seth's little sister.
When May Miller decides to shake their perfect lives up again she kidnaps the twins alongside their cousins. Claire and Seth are so worried that they would do anything to get them back. This results in Claire almost giving her live for her daughters as Jared drinks her blood in exchange for the lives of their kids. When Jared dies instead Claire learns that her blood is poison to vampires. When they can hold their girls again they hope that their lives can go back to normal and that everybody can stay safe. The most important thing for them is that their family is together and healthy.
Almost two years after the twins are born Seth proposes to Claire. She doesn't even have to think and immediately says yes.