Twin electrics

How does one charge the battery in a twin?
The logical idea seems to have the battery connected to the bus, and
both alternators supplying current (and thus power) to the bus. However
alternators have a regulator, mostly built-in, that regulates the field
so as to produce a constant voltage even if load and rpm vary. But it
would be impossible to have both alternators controlled to produce
exactly the same voltage; and as soon as there is a difference, the
greater part of curent will come from one alternator, causing higher
load and premature wear.
Is this a theoretical concern only? Does one need to install TWO
batteries, with buses normally separated, as apparently is done in (at
least some) biz-jets?
Sorry if the point is moot, or the question silly, I was just wondering.
Not that I'll be be building a twin anywhere soon...