His Majesty's Bride. - Chapter 157: Childbirth.

Violet skies, a world undergoing massive changes, a deficient moon, interlinking voids…
When the world experienced a cataclysmic event,the majority of living things ceased to exist. Although humanity survived by hiding in the last safe zones, humans had to face mutated dire beasts and colossal source beasts that could break through the space barrier and enter the earth at any second.
Luo Yunyang, a young man who grew up in those calamitous times, obtained an attribute regulator and set out to walk the path of supremacy!

- Description from novelupdates

Synopsis below:How did the Avatar universe change when a transmigrant appeared in an unknown village, long before the canonical events? And how are the two islands Kyoshi Island and Uzushiogakure no Sato (A village hidden in the maelstrom)?---Tags: AU, Before-canon, Post-canon, Violence, Death of major characters, Transmigration, Harem, Children, Incest, Romantic. Foul language.

Born and raised in a lab Tristan must figure out how to live and survive in the outside world. To make matters worse he has 4 others to look after. He's the oldest but is always being taken care of, to make sure his lab siblings want for nothing, Tristan will need to make a difficult decision. The goal is to provide for his siblings but he ends up living just like he was groomed to live. On top of everything else, there are four alphas who want to mate with him, and they don't mind sharing. Will Tristan accept his fate? Or will he runaway?