Sean is tall and medium-build, with dark hair and blue-green eyes. His skin is also lightly tanned, He tends to wear a lot of dark jeans and simple T-shirts, occasionally with a grey coat as when Rooreru first met him. He appears young for his age.
Sean has a slightly quiet personality, but he is caring and loving, and can be very emotional. He can be brave to the point of reckless or foolish, and he often acts without thinking things through fully. His judgement can also sometimes be faulty. However, he can also be cautious and distrusting, especially about being an evolved human, and is still adapting to their existence being exposed, unsure if it was a good idea or not. He basically just wants a normal, peaceful life.
HomeSean and Sinead have bought a house in New York city, since after learning that Sinead was pregnant they decided that the apartment they'd owned previously would be too small to raise a family in. Their adoptive daughter, Molly Sanders, and their four children also live with them here. The house is large and modern and beautiful. Sean came originally from a town upstate, similar to Sinead and Eoin, and the majority of his birth family still live there.
AbilitySean's ability is to sense information about the abilities of others. With this ability he can distinguish evolved humans from non-evolved humans, confirm what ability an individual has, and sense a little of how the ability functions. He can also follow the "trail" of an ability to its owner, if this owner is extremely well-known to him. He has also learned that he can detect the strengths and weaknesses of an ability, and occasionally of the individual possessing the ability.
Family and Relationships
- Mother - Catherine O'Brien
- Father - Mark O'Brien
- Older sister - Katherine O'Brien
- Niece - Sophie O'Brien
- Younger twin siblings - Maura and Lucas O'Brien
- Younger sister - Tara O'Brien
- Wife - Sinead O'Brien
- Adoptive daughter - Molly Sanders
- Daughters - Moira O'Brien, Caylee O'Brien
- Sons - Adair O'Brien, Farrell O'Brien
Sean manifested when he was roughly 20, and began sensing a difference between himself and all others. At the time he hadn't met anyone else with an ability, and he didn't know this was the difference he sensed. He met both Sinead and Eoin a year later, and sensed this same oddity within them. When he informed Sinead of this, she admitted her own ability and the 3 realised what they all had. He and Sinead began dating and eventually got engaged, when Sean was 24. After they narrowly escaped a raid from Building 26 agents, the 3 went into hiding in New York City. Sean began to make a habit of warning anyone he'd sense who had an ability, and because of this he was there to save Rooreru Juuri Kiryuu when she was almost captured. After this, she hid with the other 3 too. Along with Sinead and Rooreru, Sean assisted in the raiding of prison complexes while negotiations to end the hunting were ongoing.
Sinead and Sean moved to New York to live. After roughly 2 months of living there, Sean met Anthony Sanders and Jasper Ellis. These 2 evolved humans had realised that a group of ex-B26 agents, led by James Leit, had regained their memories and restarted their work. Ellis and Sanders convinced him to join them in preventing this group, although he was unaware when their intentions became more geared towards revenge. He only realised this when Sinead confronted him and proved to him that the others had murdered an ex-agent and his entire family, in cold blood. After this, Sean remained in the the group and attempted to bring it down from the inside, until he was discovered and captured. Sinead and Rooreru attempted to save him but were captured also. However, they were saved when Molly Sanders had a change of heart. She freed them and killed Sanders and Ellis, though they were subsequently revived and are now prisoners of the New Company. Sinead and Sean have since adopted Molly, and the couple were married shortly afterwards.
Sean helped in taking down the Carnival and preventing their attack on New York. He and Sinead both persuaded the members to turn against Samuel Sullivan and leave, by revealing the truth of how Lydia had died, and Sinead exposed the existence of abilities to the world later that day. After Aito Connell was abducted, Sean was part of the group who rescued him, and his twin daughters were born the same day. Months afterwards, Moira accidentally caused the death of Rooreru Kiryuu-Connell after she manifested her fear manipulation, and had to be negated to make Rooreru's revival possible.
Strengths & Weaknesses
Sean is strongest when he has something which he values to fight for, when his judgement isn't clouded at all, and when Sinead is there to help him and guide him and fight beside him. He also has some skill in hand-to-hand combat, and is physically strong. He's committed and dedicated, and often shows a lot of bravery.
However, his judgement can occasionally be faulty, and he has been known to sometimes choose the wrong side. He was previously afraid of being exposed as an evolved human, and is now uncertain of how other people will react to the revelation. He can be too reckless and act without thinking, if he doesn't force himself to be cautious and think things through. His ability cannot be used offensively, or defensively, as it is mainly used to find allies.
The name Sean is an Irish form of the Hebrew name John, which means "God is gracious". Interestingly, his wife's first and middle names and his cousin in law's name all share this same meaning. His middle name, Alastar, is an alternate form of the name Alistair, which is a Gaelic form of the Greek name Alexander, meaning "defending men". This could refer to how he has tried to help and warn fellow evolved humans several times during his life, including during the time they were hunted by Building 26, and later via Ellis' group. His surname of O'Brien means "from a family which is noble, strong and virtuous", and can also mean "hill".