Xombie dad after his "faked" death... Or ticking clock dad with only Hours until his disease finally buthurts him to death.
They did the latter in the JSA/Hourman comic a decade ago. Hourman could transport to a magic room anytime he wanted where his father was one hour away from dying. And he lost proportionate time he spent with pappy against his fathers dwindling life expectancy... But time froze when he wasn't in the magic room. Seeing his father was killing his father until dear old dad had to reenter time and accept his predetermined and unavoidable death from many years in his sons past.
Something similar between Hank and Johnny wouldn't be out of the question?