Seamus Ailbe O'Reilly Jr. was born in 1892 in Carlingford, Ireland to Seamus O'Reilly, son of a well respected surgeon from one of the most wealthiest families in Ireland, and his beautiful young wife, Ailbe Brigid O'Reilly (nee Doyle) following their betrothed marriage the year prior. Seamus Sr was following in his father's footsteps and studying medicine, whilst Ailbe performed her duty and birthed a son within the year of their marriage. However, there were extensive complications with the birth and she was left barren following Seamus Jr's arrival and he was destined to be an only child. He was raised in the Irish upper classes and was poised to inherit the family fortune and large estate in the Irish countryside upon his father's death. Seamus Jr wasn't, however, destined to follow in his father's footsteps like generations before him. He was born with an immaculate gift of music and by the time he was six years old, he could play the piano just by ear.
Of course, as was the tradition of his time, Seamus Jr was also betrothed, and his wife-to-be was the daughter of a wealthy American businessman from New York, Catarina Kingston. Seamus and his parents were to travel to America just before Seamus' 20th birthday, and they boarded the fateful RMS Titanic in Southampton in England on April 10th 1912, just four days shy of Seamus' birthday. They were first class passengers, and like many others on that doomed vessel, were treated like royalty on the journey. Seamus, however, a cheeky and happy-go-lucky fellow despite being the Heir Apparent to the extensive family fortune, ended up having a torrid affair with a middle class passenger, a young man by the name of Darby Franklin.
Homosexuality in those days was something done behind very closed doors and not spoken of at all. Seamus didn't think anything of the fact he was attracted to both females and males, and because he wasn't technically engaged to his wife-to-be as yet, he wanted to enjoy his last days of bachelorhood as much as he could. Under the guise of being horrifically seasick (the story he told his parents so he didn't have to accompany them to the social commitments of the journey), Seamus spent most of the journey cavorting naked with Darby in his cabin, which is exactly what he was doing when the Titanic struck the iceberg the evening of his 20th birthday.
What Seamus hadn't realised was that Darby was Kindred, stunning at that, from the Toreador Clan. As soon as it was evident the ship was sinking, Darby grabbed Seamus and held him down on the bed with Kindred strength and in a frenzy born of lust and panic, Embraced Seamus without warning. Seamus re-awakened in one of the lifeboats and in a haze, watched the Titanic sink right before his eyes, the screams of the remaining survivors something that would live on in his ears for decades to come and what he would come to use music to drown out more and more. Upon the rescue ship, The Carpathia, docking in New York City, Darby sought council from fellow Toreador in the city because he had never Embraced anyone before. He wanted to ensure Seamus' safety, and indeed the whole journey to New York City hadn't let anyone near Seamus, whom he nursed in his arms like a mother would a sick child where Seamus spent the rest of the journey unconscious. But it would prove to be Darby's biggest error. Word got back to the Toreador Primogen of the time, who ended up destroying Darby for the crime of taking one against his will and Seamus was presented to a centuries old Toreador for guidance, one Xavier Carlise, who nurture Seamus as if he was a childer of his own.
With that guidance, Seamus thrived as a Kindred and with Xavier's connections in the City, began to seriously hone his musical talent. By the time he had been Kindred for ten years, he was a musical prodigy in piano and had the singing voice of an angel with a tenor range, but piano was his true love closely followed by the harp, which he learned to play with Xavier's encouragement. Xavier had him performing all around the city, and Seamus drank it all in. His two biggest achievements were playing as the Principal Harp for the New York Philharmonic Orchestra, and the in the early 80s, playing piano in the orchestra for the first Broadway production of Cats, where he worked with Andrew Lloyd Webber. His all-time favourite piece to play and sing is Memory from that musical and it was gig with Cats that got him a permanent pianist job on Broadway, where he still is today. The Broadway network is intricate, and Seamus is one of many Kindred having their fingers in that pie.
Seamus is happy as a pig in mud in New York these days where he lives with Xavier and his mate, Gregory Kent, whom ended up becoming best friends with Seamus when they shared the same wicked sense of humour. However, he is very lonely and often wonders what love is like. He didn't love his betrothed fiancée and he hadn't loved Darby, but lately, he has been looking more and more at Xavier and Greg, wondering what it would be like to have what they have. Infuriatingly, they both tell him that he will "just know" if he ever finds it, and so far, that feeling hasn't hit him like a punch in the gut with anyone. He has fooled around with Greg's brother, Trystan and even a time or two with the Gangrel Primogen, Daniel Cooper, but it's been nothing other than satisfying natural Kindred urges.
Within a vampire bloodline known as The Kindred, seven vampire clans are collectively joined, forming the largest sect of vampires called the Camarilla, and survive through the Masquerade, disguising themselves as humans. Camarilla policy is that vampires should try to fit in with and hide from the rest of humanity, as to easily feed on them. For this reason, they created a web of lies and misinformation, called the Masquerade, to make the public believe that supernatural beings like vampires could not possibly exist. The Camarilla also believes that the only way the vampire species can survive in these modern nights is if it unite. Any breach of the Masquerade by any vampire risks exposing the entire race. Both viewpoints are fundamentally opposed by the Sabbat, an opposing sect to the Camarilla. The Camarilla also enforces the Eldest as ruling class over the younger vampires. The seven clans of the Camarilla are Ventrue, Brujah, Malkavian, Toreador, Gangrel, Tremere and Nosferatu. When a human is turned by a Kindred vampire, it is known as the Embrace, the vampire siring the human to embrace them into their own bloodline.
Each city has a ruler, a "Prince" who enforces the laws of The Masquerade that govern them to protect their anonymity. A clan is a group of vampires "related" by blood; i.e. the vampiric equivalent of an extended family or lineage. A clan is usually a large group, acknowledged widely in the vampiric society. Each clan nurture their own characteristics and traits, and each clan has its strengths and weaknesses. Often the clans do not always get along with certain clans such as the Brujah and the Ventrue actually hating one another. Each clan within a given area has a representative, a Primogen, who is usually the eldest and most powerful member of the clan, who attends the leader or prince's advisory council. This status also grants the character social advantages and greater power than being a normal member of their clan.
All information is taken from fandom source @ Masquerade Wiki and Kindred Wiki
Seamus is an original character is for kindred: the masquerade/vampire: the embraced psl, noirenewyork