There is a vase lying broken on the floor. That's the first thing he notices when he comes through the door. It was a gift from Jehan, who always brings them flowers, and got tired of seeing the carefully crafted bouquets languishing in coffee mugs, so he's a little concerned when he sees it on the ground. He calls out into the seemingly empty apartment, hoping that nothing has gone seriously wrong. "Éponine … Enjolras. What happened to the vase?" When he is met with no response, he drops his keys in the dish on a stand behind the couch, and wanders further into the apartment. He hears a small groan, followed by a smack and a yelp, which he follows into the bathroom, where he sees Enjolras sitting on the edge of the tub with toilet paper up his nose, rubbing his arm. Éponine is glaring at him with such a murderous look that Combeferre can't help but chuckle, which makes Éponine whirl around and turn the glare towards him. It's markedly less funny now, and Enjolras is looking at him with a combination of pity and terror. He puts his hands up in front of him in a desperate attempt to ward off the impending rage of Éponine. She's holding a little white stick, which she waves in his face.
"One of you fucking assholes knocked me up. There is a tiny human fucking being growing inside of me. Oh fuck…." She sinks down onto the edge of the tub, next to Enjolras, who looks at her with concern. She buries her head in her hands, and groans. "I'm going to have to stop fucking swearing. I'm going to have to be a mom. I'm going to have to make peanut butter and jelly sandwiches, and wear high heels all the time, and be June fucking Cleaver. I can't be June fucking Cleaver."
Combeferre joins the two of them on the tub, and runs his hand down Éponine's back. She removes her face from her hands, and leans against his shoulder. She murmurs to him "Why can't this thing just be half you, half Enjolras? Why does it have to have any of my fucked up genes?"
Combeferre smiles, and runs his fingers through her hair. He leans his head against hers, and tells her "You'll be fine. We'll be with you every step of the way, and there are still nine months left. We'll be okay." On her other side, Enjolras nods as much as he can without dislodging the tissue in his nose.
Combeferre studies his boyfriend before tugging on the end of Éponine's hair. "Éponine, did you…" She looks up at him with scorn.
"I did not hit Enjolras with a vase and I didn't give him a nosebleed. He started stressing himself out, and worked himself into a fucking nosebleed. I may or may not have thrown the vase at him, but it missed. It's not my fault he can handle an entire organization but can't handle the fact that I'm fucking pregnant."
The last sentence is directed quite pointedly at Enjolras, who rolls his eyes at Éponine's dramatics. Combeferre smiles at him, and goes back to carding his fingers through Éponine's hair. She nudges her head against his hand, like a cat searching for attention, and he's more than happy to give it to her, especially when she grabs him by the hand and Enjolras by his tie and pulls the two of them behind her to the bedroom.
Nine months later, they all come to the agreement that their daughter is gorgeous. Shortly after she was born, Éponine and Joly spent an entire afternoon going over dominant and recessive traits, and trying to figure out which one of them Celeste's father was. They could have gone through various paternity tests, but as Éponine so eloquently put it while holding her daughter to her chest, "I don't really give a flying fuck which one of yours she is." The sentiment of the statement was slightly negated by the following one. "I swear, if one of you doesn't get your ass in here, Jehan is going to have to get us another fucking vase."
Combeferre is exhausted, and completely and utterly fed up, but when Éponine elbows him in the side, he begrudgingly crawls over her, pressing a kiss to the side of her face, to go and try to silence their noisy daughter. They've worked out a pretty efficient schedule, and between him and Enjolras, they are able to stick to it almost religiously. And even though he's almost falling asleep at work, and Enjolras is spending a little less time on his demonstrations (Éponine was livid when she found him sitting with Celeste in the nursery, telling her stories about revolutions) and Éponine has cut down on her swearing, he's the happiest he's ever been. And he looks at his daughter, who has Éponine's hair, and his eyes and Enjolras' nose, he's certain that nothing else could be better than this.
(Except two years later he comes home, and Celeste is somewhere with Courfeyrac, and there is glass on the floor again and he can hear Éponine shouting "You fucking bastard" at Enjolras, and Combeferre just shuts the door with a smile.)