Main Story Question ( Spoiler Alert)

[Siren]

In the quest it said "When Teledji Adeledji found out Unanamo was going to step down he had to change his plans of acquiring the Carteneau Reclamation Bill so was forced to try and assassinate her to continue his plans" why would her stepping down even effect his plans in the first place

and

Who is the Thorn Family?

[AnnietheCat]

I think the answer to your first question is the fact that his bill relied on his place in the Syndicate. Unanamo abolishing the monarchy would also strip the monetarists of power and rank, and if they wanted to try and regain the power and rank they would have to essentially run for office. Like if the Queen of England decided she would try to create a democratic republic rather than a monarchy, Parliament would lose their power. As it stands, Unanamo is a figurehead at the mercy of the Syndicates wishes.

[Enkidoh]

Annie answered the first question well enough so I have nothing really more to add for that, but for your second question, the 'Thorne Dynasty' was a former rival dynastic line of Ul'dah's royal family which existed about two-three hundred years before the present day who were effectively usurpers to the throne (most interestingly, they were actually midlander hyur instead of dunesfolk lalafell like the current and legitimate Ul dynasty, as their family name suggests).

The Thorne dynasty have been referred to several times in the past in the game's story and content, for instance, the quest which unlocked Copperbell Mines early in the game referred to the Thorne dynasty as the ones responsible for enslaving the hecatonchiers whom rebelled and were sealed within the mines to die, and also during the lore behind the annual in-game festival 'Little Ladies Day', which resulted from the story of Sultan Baldric Thorne's daughter (Princess Edvya) who often tested his authority as a parent.

From what I remember, the Thorne dynasty only lasted barely a century before the Ul dynasty was restored as the ruling house of Ul'dah and effectively died out (at least, until Teledji discovered Nanamo's handmaiden Meriel was a distant relative of the family, and thus a new potential claimant to the throne).

Anyway, that's it in a kuponut shell - there was an old thread that went into detail about the Thorne dynasty and how it was connected to the current Ul dynasty, but that was before information appeared during quests in game, so it's now not really relevant.