Besides them being distant b/c of Ghost's religious anti-gay stuff vs Infinite's extra flamboyant rebelling, (like many have said but it needs to be repeated) Infinite's like 30 years old so the 'deadbeat' stuff comes off as Ghost not bankrolling his grown kid, which he shouldn't have to do anyway, regardless of his money.
Not making excuses for him though b/c Ghost is known to be awful w/ personal relationships w/ pretty much everyone and read any interview and they'll comment with how he 'lives up to his name' with his tendency to disappear where no one can get in touch with him until he pops back up on his terms.
(Again, like others brought up) his son Supreme had a falling out with Ghost that they worked through & Supreme did a song about it (verse 2):
But this going to social media with it, putting your sister's issues out there, clamoring for attention is a foul tactic and throwing more flame on those burning bridges between family for empty virtual clout and online sympathy.