A/N : I really apologize that this reaction isn't gender neutral. Its just the nature of pregnancy that disallows it, but this will be one of very few chapters where the writing is catered to only one gender!
Mark
Learning that you're pregnant would plainly and simply make Mark fall in love with you all over again. He hadn't ever realized how incomplete he felt until it had struck him that he's going to be a father. You'd told him as much, and just like that, the emptiness he hadn't known was there was filled and he was happy. He'd feel an intense rush of love for both you and the new arrival that would grace your lives in a few months. He was so, so, so excited for this, and he couldn't wait to have his own family with you. He wouldn't cry, but he wouldn't stop smiling or touching you for the rest of the week out of sheer giddiness.
"You're the best thing to ever happen to me. Look at all the happiness you bring to my life, jagi."
Jaebum
Telling Jaebum would be an experience and a half. His initial reaction would be... nothing. He'd simply stand there and stare at you, not being able to compute. He'd more than likely stay in this state until your gentle voice would break him out of his thoughts. Slowly but surely, the smile that had made you fall in love with him would start to take over his face. You'd watch as he'd cover his face with his hands, hiding that lovely look you knew too well. He was very quiet, but you watched in joy as he rocked himself back and forth, whispering about how you're going to be parents. He'd pull you in for a kiss that was very delicate compared to your normal ones, although it spoke all his thoughts. I love you, I love this child, I love that this is our child.
"Parents. We're going to be parents. I can't believe it we're going to be parents I-"
Jinyoung
Oh Jinyoung would 100 percent be a crier. Eomma Jinyoung is basically always running around, taking care of his bandmates, and so naturally he has paternal tendencies that showed you how great he was with children. So when you told him that evening over a pasta dinner, he burst into tears. This couldn't be real, could it? Being a father... it was all happening. To him. He was going to be a father and oh god the tears won't stop, but did he care? Nope. He felt like any and every dream he'd had just came true with your admission, and that absolutely nothing could bring him down. He was completely ready to embark on this new chapter of life with you, and was so excited to meet that lovely little prince or princess in nine months. He couldn't wait.
"Jagiya, this is the best gift anyone's ever given me."
Jackson
Though Jackson does like to indulge in theatrics and be dramatic here and there, that would all go out the window when you said the magic words to him. He liked being funny and energetic, but something of this magnitude could only be handled by ~manly~ crying and kisses all over your face and hands. It was the absolute best day of his life. Once you told him about the pregnancy, he'd forget everything except this moment with the two of you, and immediately yank you into a strong hug, his face buried in your neck. He'd try to get a hold of himself and wipe away the annoying tears, immediately wanting to plan. What will you name him if its a boy? A girl? What colour will the room be? Seeing Jackson so excited and happy like this just made you more confident than ever that your child was going to grow up with the most amazing father.
"Oh love, there's still so much to sort out! We need to buy a crib! The guest room needs to turn into a nursery and we definitely need to decorate it!"
Youngjae
Youngjae would let out the most ear-piercing, high pitched squeal you'd ever heard. It would be very very obvious how happy he was since he'd be jumping and waving his hands, unable to physically contain the sheer amount of joy he was experiencing. And why wouldn't he be happy? There was suddenly a reason to celebrate like never before, and he planned on partying. He'd press sloppy, excited kisses all over your face, mumbling between them how happy you make him and that you two were going to turn into three, and how it was the best thing he'd ever heard. He'd just be alight for the next few weeks, so incredibly ready for this next step that you two have taken.
"This is the best day of my life. You are the best thing in my life."
Bambam
When you tell Bambam, you tell the whole world. This bean would be so stoked that he'd scream "YOU'RE PREGNANT?" right back at you, alerting at least the entire street. This would be so thrilling to him. Its something the both of you had wanted, and it just felt so right. Like Mark, despite being a few years younger, he'd feel kind of completed. like the two of you, who had been a single unit for so long, were finally extending your group to three, and he just could not wait for the day to come. If he had loved you before this announcement (he certainly did), his love had just grown a millionfold, because you were no longer his second half; you were the mother to his child. And there was absolutely nobody else he would rather have take on that role and navigate parent hood with him. With you by his side, Bambam felt confident and right heading into this new stage.
"We're gonna be complete, finally!"
Yugyeom
Yugyeom would be, frankly, less surprised if you told him you had been a horse wearing a human costume for the whole duration of your relationship. He would not expect the announcement, taking the idea of it being a surprise to a whole new level. However, this did not mean that he wasn't happy, because this little sunshine was completely overjoyed. He'd be so thrilled to meet the new arrival. Right off the bat, he'd be excited to teach the little tot his dances and how to sing, to hold his or her hand and walk the street, to make hot cocoa in the wintertime together. There was so much he wanted to do with your child, and he was damn grateful for you and for his life for giving him this joy.
"I'm so lucky to have you, jagi. And we're lucky to have this baby. I love you, baby!"