It's a drama that probably appeared between 2010 - 2016.

Multiple generations live in the same house (grandparents, their son and his son's family, aka wife and children, not sure if there were others), the grandfather is a strict man that is never satisfied with his son's work/behavior.
One day, outside, he meets a young man that helps him out. They bond a lot and become friends (bromance). They have a lot of sweet moments together, in one scene the younger guy gives the older one a piggyback ride, or they share an umbrella (if I am not mistaken).
The grandfather actor looked like (maybe even was) Lee Deok-hwa or Woo Hyun.
Anyone knows this drama?

 MYNK:

It's a drama that probably appeared between 2010 - 2016.

Multiple generations live in the same house (grandparents, their son and his son's family, aka wife and children, not sure if there were others), the grandfather is a strict man that is never satisfied with his son's work/behavior.
One day, outside, he meets a young man that helps him out. They bond a lot and become friends (bromance). They have a lot of sweet moments together, in one scene the younger guy gives the older one a piggyback ride, or they share an umbrella (if I am not mistaken).
The grandfather actor looked like (maybe even was) Lee Deok-hwa or Woo Hyun.
Anyone knows this drama?

I don't know if  my suggestion is right........ According to what you said I found a drama with similar plot . I think it is-https://mydramalist.com/318-life-is-beautiful-2010 

Sadly, it wasn't Life is beautiful. And I haven't come any closer to finding it. But thank you, @Daya