I remember the male protagonist either transmigrate or was reborn into a weak young master body. He is the current last heir to a martial art family or a general family. His father and brothers all died at war or something. Leaving his sister in laws widows and I believe he have a kid nephew left. His grandfather I think is a old war hero with dementia and think the main lead is his son. Also, I think he have a fiancee that want to end the engagement due to his declining family and he is known as a weak or sick person. The male lead got OP in martial arts with a system or some kind of power when he start working out. I hope someone can help me find this manhua.