  Kac-Moody symmetric spaces have been introduced by Freyn, Hartnick, Horn and
the first-named author for centered Kac-Moody groups, that is, Kac-Moody groups
that are generated by their root subgroups. In the case of non-invertible
generalized Cartan matrices this leads to complications that -- within the
approach proposed originally -- cannot be repaired in the affine case. In the
present article we propose an alternative approach to Kac-Moody symmetric
spaces which for invertible generalized Cartan matrices provides exactly the
same concept, which for the non-affine non-invertible case provides alternative
Kac-Moody symmetric spaces, and which finally provides Kac-Moody symmetric
spaces for affine Kac-Moody groups. In a nutshell, the original intention by
Freyn, Hartnick, Horn and K\"ohl was to construct symmetric spaces that likely
lead to primitive actions of the Kac-Moody groups; this, of course, cannot work
in the affine case as affine Kac-Moody groups are far from simple.
