U2 Lyrics Running Still

What does this letter "from father to son The blood runs thin?
"Blood Runs fine"? I'm not familiar with this expression. What does this mean? This is a line in the U2 song "Red Hill Mining Town". Thank you. Disorder – Ah, actually, I'm a plum. How about you answer my question?
I think it was a reference to Bono's father, Bob Hewson, with Bono, who had a relationship with a little salt to the output of the track (1987). Bono wrote several songs from her turbulent relationship with his father, whose "Kite" "Sometimes You Can not Make It On Your Own" and even part of "One" is referred to Bono's father.
U2 – Running to Stand Still – Recorded at home