Tensei Shita Moto Dorei, Saikyou no Kizoku ni Natte Toshiue no Musume to Sekai Saikyou wo Mezashimas is a Manga/Manhwa/Manhua in english language, SUGGESTIVE 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

Louis, a fighter who fights slaves in the stadium. Finally loses his life in the match one day. However, the next time he opens his eyes he finds himself in a gorgeous mansion. Louis is reincarnated as the sixth son of a nobleman! And one day after more than a decade has passed, Sharon, a fellow slave from his previous life, appears in front of him. Sharon, who was a child in his previous life, has grown into an adult woman older than him――!?