A bit of backstory:
I was adopted at the age of 18 months alongside my older siblings (who were 5 and 3 at the time). The reason we were adopted was because my older sister was found to have a fractured foot while in my biological parent's custody so it was assumed they either abused her or were neglecting her.
We did not have any contact with my adoptive family for the next 17 years (until I turned 18) and I cannot remember them at all, though my older siblings can. In fact, it was often considered a 'taboo' subject to even mention the fact that we were adopted and my adoptive parents, throughout my childhood, never directly mentioned that we were adopted.
However, since I turned 18, my older sister has become absolutely obsessed with wanting to reconnect with our biological parents. This is mostly since it was because of her broken foot that we were adopted in the first place and she seems to have residual resentment. So, my sister got their contact number and has been phoning them and texting them for over a year now. I frequently overhear her shouting and venting to them about how they must have neglected her and blaming her life's woes on their actions, but also being very obsessed with wanting to know further details about our biological family. This obsession has led to my adoptive parents getting involved and them establishing contact with my biological parents for her sake, which led to the arrangement of her and my adoptive parents visiting my biological parents while I refused to visit since I don't feel any connection with them.
My sister's obsession with them has further led to them visiting our house which was very traumatising to me as I felt all of this was being imposed on me and my identity was being threatened as I don't even identify with my biological parents. But, they came anyway, and my adoptive parents encouraged them to make contact with me despite the fact that I told them not to. This is because my biological parents had been crying to my adoptive parents, telling them how much they miss and how much they want to contact me and my adoptive parents have no respect for my own feelings. So, when my biological parents visited, I locked myself in my room while my biological parents (who I viewed as strangers) were banging on my bedroom door, pleading and begging me to come out. I refused and after several hours they left.
However, unbeknownst to me, they secretly agreed with my adoptive parents to see me when I did not expect. This happened as the next morning (since they were staying at a hotel over the night), they came to our house but hid in their car behind the bend. Then, my adoptive parents tricked me into coming out of the house to get into our car, saying that my biological parents had left and weren't returning so it was safe to do so. But, just as I entered my adoptive parent's car, my biological parents burst from behind the bend to meet me. These strangers, who I had never seen before, started throwing themselves on me, while I begged my adoptive parents to drive off, which they eventually did but only after a few minutes of trauma had passed.
Over the next few months, my sister has continued contacting them, and thanks to her, they keep pressuring my adoptive parents to force me to reunite with them and my sister, who is still so obsessed with them keeps on bringing up the topic of our adoption. She constantly asks questions to our adoptive parents about our adoption, discusses her interactions with our biological parents and this stresses me out because again my identity of being completely happy not having contact with my biological parents; being fine with my adoption etc is threatened as this keeps being brought up.
Now, my adoptive parents are angry that I am not meeting with my my biological parents. This is largely due to the fact that they want to maintain 'face' and because they have issues with their own families of not having good relationships with them so they think that it is necessary for me to have a good relationship with my biological parents.
For context I am now 19 and still financially dependent on my adoptive parents.
Also, my adoptive mother is very narcissistic and if I am being honest, I think she sort of secretly loves the attention this brings her. For instance, when my sister bangs on about our biological parents, she will ask me 'Do you want to go back to them' and when I inevitably say 'no' she will slyly grin as though it means that I love her so much and she is so important. But, the reality is I am increasingly resentful towards her and my adoptive father and my sister due to the forcing this on me. And everyone seems to forget the fact that I do not hate my biological parents or love them - I am just indifferent and I do not want strangers imposed on me.
So, based on all of this who do you think is at fault and what should I do?
For reference, my biological parents are now discussing spending summer with us by visiting us since my sister wanted them to come over so much and my adoptive parents felt they could not say no and are now pressuring me to be happy about the whole situation.