Remus Lupin works at NASA, content with his quiet routines, until Sirius Black arrives and disrupts everything. What begins as dislike, shifts rapidly into something far more intense. But Sirius is struggling, and as his mental health begins to fracture, the relationship does too. In the aftermath, Remus finds an unexpected friendship with Regulus Black, Sirius’ semi-estranged brother, just as tragedy sends everything spiraling.
This is not a story about space.
It’s a story about gravity.
About two people falling together, and what happens when one of them slips away.
NSFW - TW:
This story contains explicit sexual scenes, graphic depictions of self harm, mental health struggles, death, and heartache.
Please remember to read all tags before starting any of my fics to avoid triggers or content you are uncomfortable with.
Please take care.
If you are in crisis or need support please reach out to the crisis text line in your country or emergency services. 🖤
I’ve been meaning to write a post about Borderline Sirius for the longest time, but this is partly inspired by my posting a snippet of a BPD!Sirius fic a while ago and the fact I’ve had this headcanon for over two years now. My Sirius is often written as being Borderline, whether explicit or not. Borderline Sirius is something I’ve become increasingly attached to recently. The more I look at his personality and actions in canon, the more I can see him attached to the criteria of BPD/EUPD. A lot of my feelings about Sirius are from my own personal canon, especially during the First War where the pressure pot of existential dread is an untold stress on all members of the Order, but I think especially Sirius struggled under this pressure due to his personality disorder.
I think the easiest and most structured way to talk about Sirius’ Borderline—which is a complex and deep set of characteristics rooted in trauma and a consistently disrupted childhood, as all Borderline is—is through the diagnostic criteria from the DSM V. To be diagnosed with BPD, one needs to show at least five of the criteria. For ease of reading and to avoid a 3k word text post, I’m going to expand on the ones I think Sirius shows the most and leave others as a few lines.
This should go without saying but here we are, these opinions are my own and do not invalidate or disprove any other headcanons anyone else may have—everyone’s Sirius and their interpretations of him are all valid! If you don’t like my headcanons, DNI and move on!
A note on Bipolar Disorder v Borderline Personality Disorder: I’ve seen both use the same acronym and for ease I’ve taken to saying Borderline rather than BPD, or using the new acronym of EUPD (Emotionally Unstable Personality Disorder). This post is also partly inspired by seeing @soloorganaas’ posts on Bipolar Sirius on my dash in that we need more psychological deep-dives into these characters, looking at their mental illnesses and neurodivergencies outwith canon. That is to say I love Natasha’s posts on Bipolar Sirius and you should all go and read them! Bipolar and Borderline aren’t mutually exclusive and, of course all headcanons exist at once, but in my own experience both Bipolar and Borderline have many overlaps, especially in Sirius’ character.
If you have things you want to add to this post, please feel free to reblog. Though I would kindly discourage any Borderline-bashing, if you have nothing nice to add, DNI. My dream would be to open a discussion about Borderline Sirius and other Black family members who we may headcanon as having BPD—because let’s be real, it’s a family heirloom.
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Frantic efforts to avoid real or imagined abandonment.
I think this is the most painful thing to think about because of all the abandonment Sirius has suffered throughout canon. What I think of first are the two-way mirrors; Sirius and James are so very intertwined that they want the ability to communicate at any given moment, even during school. Frantic efforts to avoid abandonment can be demonstrated in several ways, both in clinging to the person, or abandoning the person first in order to paradoxically avoid the hurt of eventual abandonment. I think this is part of Sirius’ reaction during OotP, when he pulls away from everyone due to their perceived abandonment of him—he is alone in the house of his childhood and his friends are leaving to go and do the work he wishes he could do.
2. A pattern of unstable and intense interpersonal relationships characterized by alternating between extremes of idealization and devaluation.
For me, this is the peak of explaining Sirius’ behaviour throughout canon.
I hesitate to call it the Prank because that word isn’t used during canon at all, but for ease of understanding, I will. Borderline patients can have episodes of hypomania, and I do think an episode of mania contributed to Sirius’ actions here, but I also think Sirius split on Remus—ie, his perception of Remus switched from idealised to demonised and devalued. This could be over something so seemingly trivial to an outsider, even something like choosing to sit next to James and not Sirius at the dinner table, or not replying to a note Sirius passed to him. I can see Remus doing something that makes Sirius devalue him to the point of Sirius not seeing how the following events will affect his friend and he sends Snape to the Shack in a moment of impulsivity (more on that later), without truly being cognisant of the consequences of his actions, because he, in that moment, did not see Remus as a person of value.
He absolutely idealises and idolises James Potter (he is Sirius’ Favourite Person—something I could write a whole other post on) and Sirius’ idealisation blinds him to any more sensible actions especially regarding the Fidelius charm. He will go above and beyond to protect James and his family by extension. Peter, and also Remus, are so idealised by Sirius that they are able to do no wrong—perhaps this is why Sirius is able to overlook any slight clues as to Peter’s true allegiances and entrust him as the Secret Keeper.
Harry, by extension, is hugely idealised by his Godfather. Sirius believes he is perfect and that Harry can accomplish anything. When Harry sends his letter in GoF saying his scar hurts, Sirius immediately flies back to protect him, and also breaks into a Wizarding house to use the fire to communicate with Harry. Harry is not above being devalued by Sirius, however: in the Floo-call in OotP, Sirius tells Harry ‘you’re less like your father than I thought’, and to me it’s clear in that moment that Sirius sees Harry as having fundamentally missed the bar of high standards Sirius holds him to.
3. Identity disturbance: markedly and persistently unstable self-image or sense of self.
As we know, Sirius was the first Black not to be sorted into Slytherin. I think part of that comes from Sirius’ unstable sense of self, which, according to several studies, comes from the inability to integrate positive and negative traits. Sirius was simultaneously idealised by his parents and family as the scion of the House Black, and then, when he began to not meet their standards, was devalued as a blood traitor. I believe that Sirius developed some dissatisfaction with his life before he was sorted into Gryffindor, which was only heightened by his sorting and then devaluation by his family. This gives Sirius a markedly disturbed sense of self, which I think we can see during PoA where Sirius’ entire personality becomes getting revenge on Peter, then swiftly switches to being Harry’s Godfather once Peter has been caught.
4. Impulsivity in at least 2 areas that are potentially self-damaging. (e.g., spending, sex, substance abuse, reckless driving, binge eating)
Sirius’ recklessness is well characterised in canon, imo. Simply put, he spends recklessly—the Firebolt for Harry—and we are well aware of his substance abuse during OotP. We see his recklessness during PoA also, where he comes to Hogwarts despite knowing that there are Dementors and Aurors looking for him, because he wants to find Peter. He also breaks into a Wizarding house during GoF in order to Floo-call Harry, which obviously could potentially end badly.
As above, I also think The Prank is a symptom of Sirius’ impulsivity. Borderlines often say and do things in the heat of those splitting moments which can be self-damaging in more than the physical ways listed above, such as ending friendships or starting arguments, and I do think the Prank is damaging to Sirius’ view of himself, his position within the friend group of the Marauders and especially his view in James’ eyes, regardless of whether the Marauders forgave Sirius quickly or not.
5. Recurrent suicidal behaviour, gestures or threats, or self-mutilating behaviour.
Okay, this isn’t explicit in canon, but I do think Sirius’ actions at the Department of Mysteries are part and parcel of his suicidal ideation. This passive devaluation of his own life leads him to put himself in danger for Harry—who becomes his FP in James’ absence—and his recklessness goes beyond the above criteria. His escape from Azkaban in PoA is similarly reckless. No one has escaped Azkaban yet Sirius, who has spent twelve years punishing himself for the death of his FP, is willing to try, such that he values his life so little.
Admittedly, this criteria is also largely based around my own headcanons especially during the First War. I believe Sirius’ recklessness with his own life is marked during this time, especially if anything should happen to the other Marauders, Sirius’ internal monologue may often turn to suicidal ideation.
6. Affective instability due to a marked reactivity of mood (e.g., intense episodic dysphoria, irritability or anxiety usually lasting a few hours and only rarely more than a few days).
Ooh, this is a big one. I instantly think of Sirius’ immediate, marked happiness when Harry says he would like to come and live with him at the end of PoA—everything else is immediately unimportant when Sirius’ Godson (and Favourite Person) is talking to him. When Harry first arrives at Grimmauld Place in OotP, Sirius is jovial if a little concerned about Harry, but playful nonetheless. This changes very abruptly when Molly raises concerns about Harry being brought up to speed about Voldemort. We also see Sirius in a depressive state when he is told not to accompany Harry to his hearing.
7. Chronic feelings of emptiness.
How else would he survive the emptiness of Azkaban if he didn’t already know how that emptiness felt? Welp, I’m giving myself feelings.
8. Inappropriate, intense anger or difficulty controlling anger (e.g., frequent displays of temper, constant anger, recurrent physical fights).
*gestures vaguely at the whole Shrieking Shack scene*
Beyond that, Sirius’ fury during OotP when he and Molly argue is also important here. I want to note also the difference between hot anger and cold anger, in that I think Sirius is very much feeling cold anger in this moment when he is arguing with Molly. Although I largely headcanon Sirius as experiencing a lot of ‘hot’ anger—that is to say, shouting and yelling, red-faced and furious—especially during the First War, I do think that being in Grimmauld Place in OotP makes Sirius lean towards ‘cold’ anger—more calculating, more biting and sharp—like his anger when Harry questions him about the Family Tree and when he and Snape argue over Harry’s Occlumency lessons. Perhaps we don’t see ‘hot’ anger from Sirius often during OotP, but we do see plenty of ‘cold’ anger from him, as well as a healthy dose of resentment and bitterness.
9. Transient, stress-related paranoid ideation or severe dissociative symptoms.
Sirius’ actions and reactions in OotP are classic, imo, dissociative symptoms, specifically being back in the house where large amounts of his childhood trauma and the seat of his personality disorder took root.
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Overall, I think looking at our favourite characters through these psychological lenses really changes how we interact with them, both in canon and fandom settings. There are so many great takes about what it means for these characters to be neurodivergent in many different ways, and I’m sure there is a whole host more to say about Sirius’ mental health, whether he be Borderline or not, that I won’t cover here because this is going to be over 2k words.
If you made it to the end, I salute you! Thank you for listening to me ramble about Borderline!Sirius and how dear he is to me! 🖤
For some reason I like to imagine that Sirius had BPD (Borderline Personality Disorder)
Frantic efforts to avoid being abandoned by friends and family.
Unstable personal relationships that alternate between idealization—“I’m so in love!”—and devaluation—“I hate her.” This is also sometimes known as "splitting."
Distorted and unstable self-image, which affects moods, values, opinions, goals and relationships.
Impulsive behaviors that can have dangerous outcomes, such as excessive spending, unsafe sex, substance abuse or reckless driving.
Suicidal and self-harming behavior.
Periods of intense depressed mood, irritability or anxiety lasting a few hours to a few days.
Chronic feelings of boredom or emptiness.
Inappropriate, intense or uncontrollable anger—often followed by shame and guilt.
Dissociative feelings—disconnecting from your thoughts or sense of identity, or “out of body” type of feelings—and stress-related paranoid thoughts. Severe cases of stress can also lead to brief psychotic episodes.
