In RainbowDoubleDash's Lunaverse, Night Light refuses to believe that Twilight could have done anything wrong. He sees his daughter's fugitive status as being entirely Trixie's fault — it's actually both of theirs — and is entirely willing to let Ponyville remain in ruins to get back at the latter.At the Grand Galloping Gala, Ditzy calls him out on it by using her own motherhood to give herself the high ground and deflect his attempts to use this.
In The Masks We Wear, Zuko refuses to betray his father despite the fact that he (Ozai) burned him.
In Blood Is Thicker Than Bone, Kimimaro is torn between staying loyal to Orochimaru, his master who gave his life purpose again only if it meant being his next body and the last remaining relative and family he has, his cousin who both recently discovered that the other existed. During the attack on Konoha, he makes his decision and chooses to aid and fight with his cousin Naruto
Corrin: Look little girl, I've seen enough blood to know that it all looks the same. It's all red, and you only ever see it when things have gone horribly wrong for the person holding it. It keeps the body pumping and makes a big mess when it gets spilled, and beyond that I don't see any reason to attach any sentimental value to it. True family is the people who have been there with you through thick and thin. They're the ones who make you feel warm when the world seems cold; the people you grow with, train with, eat with, you fight with and laugh with over the stupidest little things. That's family to me.
Averted in Laurel Lance Character Studies, where Thea displays more loyalty to Laurel than to her brother Oliver. To the point that she outright states Laurel deserves better than him; and after (repeatedly) begging Laurel to "scream about what an ass my brother is" Laurel's confessions/rants make Thea angry enough to avoid Oliver for days. Although a case could be made that she is choosing family, it just isn't her blood.
Subverted in Neither a Bird nor a Plane, it's Deku!. Even after learning about the wonders of Krypton and his biological father's efforts to save him from his planet's destruction, Izuku can't help but feel a stronger connection to his adoptive parents than his birth parents. As far as he's concerned, the Midoriyas are his real parents.
Izuku: I-I mean, my mom and dad didn't make me, but they're the ones who raised me. They're the ones who taught me right from wrong. They're the ones who always tried to make me feel okay with being, well, me. Jor-El and Lara Lor-Van gave me life, but as far as I'm concerned, Inko and Hisashi Midoriya are my real parents.
Discussed and subverted in Only Flowers Fall. Lillie disowns her previously abusive mother but others, including her brother Gladion, tell her she should forgive her because they're blood. Even Lillie is confused on what she should do until her maternal figure Professor Burnet explains that she shouldn't forgive Lusamine just because they're related.
Youre being cruel, they say. Shes your mother, and youre her child. You need to reconcile someday, so why are you holding back? She told you that shes sorry. What more do you want? (You want your childhood back.)
In Karma in Retrograde, Touya is initially terrified of meeting with his siblings, fearing that they'll hate him after learning what he did as Dabi. While they don't condone Dabi's actions, Fuyumi and Natsuo are both glad to have their brother back for however long they can.
Touya:[more nonchalantly than intended] Hey, Fuyumi. Fuyumi:[hysterical] "Hey"? You vanish out of the blue for four years, apparently become a villain that attacks our little brother, and then get turned back to a teenager - and all you can say is "hey"? Touya:[ashamed] There really isn't much I can say besides I'm sorry. [drops his gaze to the ground] I dont know why I left or why I became what I did, but I- Fuyumi:[wraps her arms around him and sobs into his shoulder] Youre back. Youre really back. I used to dream of it, but you just vanished and I Touya:[voice cracking] Im sorry for leaving you alone, but I'm here now.
A Thing of Vikings: Justified, discussed, subverted, exploited and defied, all at different times throughout the fic and with different situations. It's justified in that blood ties are seen as incredibly important, and there's an intricate web of them tying the various clans of Berk together to allow them to bypass debt claims and get on with the task of surviving, Cami is allowed to keep a dragon she accidentally bonds with because she has a blood tie to Berk through her father, and Hiccup gives Snotlout support when he leaves for the Roman Empire because they're cousins. It's also discussed by Bladewit to Fishlegs as an important bond that keeps the clans at least somewhat united—but that bond is under strain. And blood ties via marriage are seen as more of a guarantee against attack than any form of treaty, resulting in Wulfhild becoming Hiccup's concubine, as a surety for Norway's chiefs against dragon-rider attack. It's also subverted, because the Jorgensons were trying to use Snotlout's blood tie with Stoick as his nephew to supplant Hiccup as heir, Dogsbreath steals from his father and shaves his beard because of a dare from a girl and they end up running for it, Mildew wants revenge on his estranged brother, and John the Orphantrophus counts on this trope to keep power, only to lose control when his newly Imperial nephew turns on him on his first day as Emperor. Alvin exploits it to guarantee his spies' loyalty, by keeping their family members as insurance. And finally, it's outright defied—Heather wants to kill Dagur, her brother, for killing their father.
Tellingly, Chapters 30 and 31, the chapters that show Hiccup and Astrid's wedding, are called "The Blood of the Covenant Is Thicker..." and "...Than the Water of the Womb."
In Where Talent Goes To Die, Sugiura expresses a surprisingly practical and non-sentimental version of this. While she doesn't get along with her parents or siblings, she would never let them die, and would like to think that they'd be as willing to look out for her. She explains that while people can't choose their family, and people often do terrible things to family members, "you've got to look out for your family, because if you don't, who will?"
The Bridge: Defied with the Godzilla Junior, whom was adopted and raised by a human mother he imprinted on and then Godzilla Senior, which had no genetic tie to him outside of being the same species. The assumption he yearns to find his birth parents to find out why his egg was abandoned so he can know his "real family" is brought up a few times and shredded. He holds no ill will to his biological parents, but is entirely apathetic to finding them or seeing if they are still alive. To him, Azusa and Senior are and were his "real parents".
This is one of the main themes of The Black Sheep Dog Series. Sirius is told by his Cool Uncle Alphard that no matter how much he hates his family and try to deny their blood ties, he can never change the fact that he is a Black. Indeed, despite having run away, Sirius is still living off on his family's wealth (i.e. the inheritance he got from Alphard), and the readers see that, despite his defiance, he is still very much Not So Different from the rest of his clan. He also gets surprisingly defensive when Frank accuses his parents as being Death Eaters.