I love consistency and congruity. But in this case it really is inconsequential to the question or answer how many Gs there are. I say let the author of the question or answer decide on the convention they want to use to describe how many greats or Gs their ancestors had.
I'm all for improving readability, so if there are lots of Gs and it's distracting, then by all means edit it. But if it really doesn't make any difference to understanding the question, then let the post author use the convention of their choosing.
We have to be careful not to edit the original author's style too much, as I've seen on other Stacks people get offended by minor stylistic changes. These days I try to limit my edits on questions and answers to spelling and grammar, occasionally breaking up large paragraphs or adding lists when useful.
Bottom line: if it doesn't substantially improve the question, leave it be.