This request specifically asked for Zero, Marina, young Harlock, Daiba, and Kei. So this is one of those "AUs where everything is the same except..."
Also a little bit of Harlock/Zero.

I told Marina we didn't need to dress up for a dinner with Harlock, but she insisted. I think she wanted to show him up in some form out of spite for being dragged onto his ship. So while I showed up in nice slacks and a button-up, Harlock wore his usual blue suit. At the sight of me, he snickered.

I shoved the bottle of wine we brought into his hands. "Come on," I sighed. "Let's make this as painless as possible." Marina and I didn't have a choice. We owed Harlock. He gave us the tip that led us to the capture of our last target, and in return we agreed to Christmas dinner on the Deathshadow. I never would understand his motives.

"We'll have fun if you just relax," he said as he led us to the table set up in his cabin. Tochiro was nowhere to be seen, but two children already sat there. The smaller one, a boy no older than ten, shoveled cranberry sauce into his mouth. "Tadashi," Harlock warned. "I told you not to start eating yet."

The scrawny blond boy dropped his fork with a pout. Across from him sat a lanky girl who could have been his sister, maybe fourteen. She greeted us with a smile and a wave. Harlock turned to find me glaring at him. "Why are there children on a pirate ship?" I asked.

"Well you know." He shrugged. "We found them, so we brought them along."

I blinked, feeling so flustered I forgot how to speak for a moment. Marina spoke for me. "What?"

"Introduce yourselves," Harlock told the kids.

"I'm Kei Yuki," the girl said before pointing to the boy. "That's Tadashi Daiba."

I reached up to tip my cap at her, only to find empty air. My hand flitted back down as I remembered I wasn't wearing it. "My name is Warrius Zero," I said. "And this is Marina Oki. I'm sorry, but how do you two know Harlock?"

"I wanna eat!" Tadashi howled. "I'm starving!"

"You ate a meal like an hour ago," Harlock said. I remembered that tone. He sounded so much like I had when dealing with a screeching child, worn down from exhaustion.

I still needed an explanation for where these children came from, but Marina and I took our seats to get dinner going before Tadashi started eating the tablecloth. Harlock poured wine for the three of us, while Tadashi used both hands to tip his milk glass toward him. Kei sat silently, the most polite child I'd met sitting across from the grumpiest.

"But really, Harlock," I said as he sliced up the ham. "Where did these kids come from?"

"Earth." He passed a slice to Tadashi, who proceeded to eat it with his hands. Admittedly, he was a cute kid, though he desperately needed a haircut for that bird's nest falling into his eyes.

Harlock appeared to treat them well, and there had to be a reasonable explanation. "You know I'll have to take them out of your custody if you don't give me some straight answers," I said.

Kei said nothing but eyed me with a sharpness that rivaled Marina's gaze. Tadashi looked ready to go for my throat, but a smirk eased onto Harlock's face. "Look, I know you're a sucker for kids, but these ones are mine fair and square. If you want to steal them so bad, you can just stay here with me."

As I tried to process whatever he was talking about, Tadashi smacked at my arm. "Mister," he demanded. "Are you a pirate too?"

I threw Marina a curious glance, wondering how safe revealing our title to children could be. She shrugged, brows furrowed in confusion. "No," I said. "I'm an Independent. I work for the Earth government."

Something about my second statement made Harlock's eyes widen and lock on his small charge. A forkful of potatoes froze a few inches from his mouth. At the same time, Tadashi's face reddened. He appeared to be holding his breath and was about to turn purple when Kei spoke. "Tadashi doesn't like the government," she said.

The boy let out his breath just to scream at me. "They're the worst! You're horrible! Go away!" Tears welled up in his eyes, and his lips trembled. I couldn't stand to make children cry, and my stomach twisted at the sight. Harlock appeared to share my feelings.

"He's not like them, really," Harlock said in a rush to get an explanation out. "Zero is a great guy. He kind of works for the government, but he's not one of them. He acts more like a pirate than one of those lazy bastards."

Marina threw a disapproving glare his way, either because of the swear or comparing us to pirates. I worked on recovering from him calling me great.

Fat tears rolling down his cheeks, Tadashi rubbed at his eyes and sniffled until my heart couldn't take it. "The government does some bad things," I said. "I don't agree with everything they do, but it's my job to keep space safe for travelers and to help Earth rebuild." Careful not to scare him off, I reached out to ruffle his hair.

Shimmering eyes peered up at me from behind his hands. "I think he's okay," Kei said. Harlock backed her up with an affirming nod, and that was all it took for Tadashi. Once he cleared his plate, he crawled into my lap and let me wipe the food from his face with a napkin. Harlock stared at the two of us, chin in his palm and a warm smile on his face. Marina eyed Harlock with suspicion. Kei didn't appear interested in any of us.

By the time we finished the wine, Tadashi slept against me with a gentle snore. A flush dusted Harlock's cheeks, possibly from the second bottle of wine he opened for himself. While Marina instructed Kei on how a ship should be run, Harlock scooted over to take Tadashi's seat beside me.

"You really are good with kids," he hummed. A drunken smile warmed his face. "I heard the Earth kids loved you. Nice to know the rumors were true."

I couldn't imagine why he would hear such rumors about me. "They hated me for a while after the war," I murmured. "Glad things have turned around for the most part." Tadashi sighed in his sleep, so I reached up to run my fingers through his hair. Despite its appearance, I caught no knots.

A gentle weight appeared against my shoulder – Harlock resting his temple against me. "Okay, but you can't give him more attention than me," he said. "Gotta brush my hair too."

I shrugged my shoulder to bump him off. "You get enough attention, and I don't need to spoil you anymore than you already are."

Never one to be put off, he leaned his face in closer to my neck. "You should stay here. We can raise the kids together, and I'll spoil you too."

Across the table, Marina blinked at the tipsy pirate with one brow raised. I did my best to lean away from him as my neck burned in a blush. "Harlock," I huffed. "I'm taking the kids back to the Karyū."

"Nah." His arms snaked their way around me and Tadashi. "Those are my kids, but you're welcome to share."