This assumes parents would vote in the interests of future adults. In my experience, parents are quite happy to vote against future adults, even their own. Housing policy is the most obvious example.

Is that a reference to one of the sources of the civil war in the US? Voting rights for disenfranchised (literally enslaved) people?

Actually the US maintains a Senate and Electoral College because of slavery, and refuses to abolish them for (supposedly) any and every other reason. These systems allow whites in less populous states to exercise outsized power.