hi ! i just saw your … post about regulus being the brother-in-law who literally decided to get his brother’s wife pregnant because yes yes sirius is so mean to his wife and regulus decided to take care of this issue. i just want you to write how sirius will react if he sees the belly of his wife being a bit round than usual… then he finds out she is pregnant… and so he knows she cheated on him ? then he forces her to tell him who is he ? pls pls
I feel like Sirius would have two very different reactions, depending on his relationship with his wife. If he doesn't care too much about her, I feel like he probably won't care if she gets pregnant by someone else, actually, he'll prefer it, because that means he doesn't have to interact with her anymore. But if Regulus actually talked with Sirius about how bad of a time you were having with the marriage, I do see him trying to approach and at least befriend her, ultimately falling for her.
If that is the case oofff… she is in for a whole new husband. The previous cold and not caring man that would use any and all excuses under the sun to leave their house is suddenly friendly. Not only friendly but flirty. Actually spending time with her, talking with her about anything and everything, favourite hobbies, passions, ideas for their life… He starts to see her as a person, not just as a pawn his parents used to force their ideals onto him. So when it's been months since the wedding, and just a few weeks since Sirius has started talking to her, not having touched her before in a sexual way; maybe stealing a kiss or two, she starts showing a little baby bump he gets angry. And if Sirius Black is one thing is impulsive, so he pins her down on the nearest surface and, holding her face impossibly close to his, with murderous eyes he spits "Who did you fuck?" which leads to her crying and apologising. And mean!sirius (my love) just goes "If you're as sorry as you say you're going to suck me off and let me fuck you like I should've all these months ago"
And as he starts pounding as hard and as rough as he can into her from behind, because "he doesn't have to be gentle with a slut" he just keeps repeating: "Who was it? Hm? I'm not letting you cum until you tell me who fucked my fucking wife." And when she finally tells him; he stops, turns her around, dries her tears and just mockingly says something along the lines of "Oh, my poor little wife, I was being so mean she had to go fuck my little brother to get an heir. Were you really that stressed? Oh, my poor baby, I'm sorry I was so mean, but you're still a little slut for fucking someone else that's not your husband."
I think he'll mostly act out of anger because he realized that his wife is actually great, and he was a dick, and now he's not the one to give her a baby/heir. He'd definitely fight Regulus after he's done with his wife.