The Higher ups wants you gone.

You were born in a small clan of sorcerers in that clan, the clan head(s) had wanted to be acknowledge by the higher ups as one of the clans like the zenin, gojo and kamo. Your father was the new clan head and like the clan head(s) before him, wanted the same acknowledgement and because of that He had married with someone with a strong curse technique and potent curse energy.

before you, your three older siblings were born then you were. your father had hoped that you and your his siblings would develop a strong cursed technique since their mother has powerful technique called Angel's Curse. when your siblings Curse technique did develop, He was pleased due to being Powerful in their own right but your Curse technique never seemed to show, it disappointed him and it didn't help that you haven't showed signs of having Curse energy as well but he still hoped you were just a late bloomer But that Hope turned to Disappointment over the years. you were a "Non Sorcerer" and disowned because of it.

but you did developed an Curse technique shortly after you were disowned, this Curse technique nullifies Curse energy even your own and it erases Curse Spirts within a certain reach of you, this Curse technique's range also gets larger and wider the older you get. This curse technique was named Devil's Blessing by your mother after she find out about your curse technique since her Curse technique works oppositely compare to curse technique.

because of this the higher ups decided to send you to execution.

(My notes. okay so uhh... I haven't seen JJK yet so there's one big fat chance that I might mischaracterize him. The timeline is also sometime during the first arc)