Daniel Adams and Sir Galahad were married in a private agreement between the two of them sometime in 1896, twenty years before Daniel died from tuberculosis.
From the beginning, they were an odd couple. The two met in a molly house that doubled as a meeting place for magically-affiliated people. Daniel, a half-angel demon hunter with extraordinary marksmanship and somewhat extraordinary healing powers, and Galahad, a semi-retired immortal knight and Caretaker of the Library, both seemed to hit it off well when they quarreled flirtatiously over a seat at the bar. The two soon became partners in fighting magical phenomena, Daniel focusing of course on demonic entities while Jenkins continued to aid the Librarian at the time.
Daniel's death transported his soul to hell, where he would spend the next century.
Galahad spent the next century in a spiral of both merrymaking (read: clubbing) and isolation as he flitted in and out of the Library at a whim, eventually culminating in a decision to stay isolated, working on artifacts and later aiding the Librarians.
And then Daniel returned. Traumatized, but now a full-fledged angel, Daniel sought out his husband to make sense of his new life on Earth. Though conflicted over his loss, Jenkins took it upon himself to care for Daniel until he could adjust to his new life and cope with his trauma. The two were later married again, this time in a public ceremony.
Now they are figuring out how to navigate life as the people they've become, but with fundamentally the same occupations as they had when they first met. Don't worry, they'll figure it out. They only have forever.
It's a tale as old as time. Boy meets girl, boy is an immortal knight destined to live to the end of time, girl is destined to die of a brain tumor in a few years' time. Aside from that, they have a lot in common. They both love tea, and books, and magic -- especially magic.
After a failed attempt to ask him on a date, and the departure of Charlene from the Library, the two began to reconsider their relationship. As much as he had felt for Charlene, Jenkins realized that his grief over the past would not benefit him in the present, so he decided to act on his love for Cassandra. This time, Jenkins decided to ask Cassandra out for sushi: a real-life honest-to-god official bona-fide date.
Still, there are a lot of obstacles for the two of them still to navigate, like their stances on the use of magic, Jenkins' on-and-off ability to show affection, and Cassandra's still-impending mortality.
Galahad has been in love with Cassandra for ages. No, literally, ages.
Fate has drawn Cassandra and Sir Galahad together over several lifetimes, all of those lifetimes being Cassandra's. Different incarnations of her seem to keep running into Galahad, but neither of them know it. Will either of them figure it out in this lifetime? Well that's kind of the point of this verse, we hope.
Cassandra and Jenkins never did get together themselves, but they support each other as the best of friends. In verses where one or both of them has a significant other, they attend each other's weddings and Jenkins keeps crying because he's just *sniff* so proud.
Olivia Jones (Soto) and Jenkins met when her adoptive brother, Ezekiel brought her to the Library in an effort to help her to control her powers. Her ability to conjure flames at a whim made her dangerous despite her best efforts, resulting in an extended stay at the Library despite her non-librarian status. Jenkins, the bearer of his own magical powers, decided to take her under his wing, teaching her to control her fire via the "rules" of magic (if such a thing could be said to have rules). He acts as a pseudo-grandfather to her despite his reluctance to take such a title and will eventually gift the girl her very first sword. When she's much, much older.
Cue lesbians with swords joke.
Virote can occasionally be said to drive Jenkins up a wall. As the grandson of Mercury, he faces his own wall of heightened family expectations and occasionally visits the Library just to get a break. Jenkins acts as his confidant and a bit of an advisor, though the value of his advice can vary. Usually he ends up telling Vi to stop overworking himself so damn much. Witches gotta stick together.