When The System Opens After The Age Of 100 , All Grandchildren Kneel Upon The Mountains! is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Xiao Chen, a time-traveler nearing the age of one hundred, was peacefully preparing to spend the rest of his life. Suddenly, a system activated, rewarding him for his family’s childbirth. Not only would he become stronger, but his lifespan would also reverse! “Procreate, quickly procreate!” he exclaimed. “Everyone in the family, regardless of age or gender, give birth, give birth, give birth!”