It is basically confusing an uncle with a grandfather, or an aunt with a grandmother.

These languages are indeed relatives, literally part of the same family, but we usually distinguish whether they are lineal ancestors or not. If you said "Julia is your grandmother" when Julia was actually the person's aunt, that person might get very confused about your claim!

People's aunts do often have a cultural effect on them, but we can still be more specific and distinguish them from their grandmothers.

No, the succession (Sanskrit, Greek, Latin, post-Latin) was given mainly in terms of the apogee - one peak follows the other in time. When I wrote «Sanskrit entered into Greek, Greek into Latin, Latin into English» I described the phenomenon, not the fact.

The literal matter (of direct inheritance) was meaningless to me in the composition, because the whole point was not and is not "what took from what": the whole point is the contribution that those languages give in the understanding of the current languages they informed.