Strongest Survival by Otome Game’s Heroine (LN) - Vol 3 Chapter 15: Intruder

This is a story about the protagonist getting the system, going crazy in the biochemical apocalypse, producing aircraft and tanks, destroying zombies, saving good people and killing bad people.

- Description from novelbuddy

Yao Tang, the daughter of the Yao family who mistakenly exchanged at birth, was finally found.

Maid, older sister, younger sister, and even mother, all of them.

Roland died and transmigrated into the body of the third son of a Baron. Having reincarnated, at first he looked forward to the grace of the system or any other golden finger; alas, it seemed not everyone was lucky.In the end, he accepted that those were fantasies, whereas this was reality.Being the third son, he couldn't inherit land according to laws; however, he had a bit of warrior aptitude suitable to become a knight.Knowing that this might cause trouble in succession later, his father enrolled him in the army.Several years later, he became a 3rd-rank knight in the Beginner Stage and was going to be promoted but was injured when he tried to save the commander of his battalion.Amidst that, he received shocking news about his family's demise due to a monster tide, leaving him alone to inherit the barony.Weighing the pros and cons, he decided to escape from the risky venture and settle in a poor backwater barony village to lead a peaceful life; however...Just when he thought it was over, he awakened the Children's Blessing System.[Host's child detected, Family System activated.][Begin testing the child's aptitude.]“What, for real?”