Can several owners hold the same fraction?

Yes, several owners can hold rights in the same fraction. The most frequent example being the one of couples who are co-owners of a fraction. However it is forbidden, except for provision to the contrary in the declaration of co-ownership, that several owners share the right of enjoyment periodically or successively ("Time Sharing"). Owners can thus acquire a fraction in indivision but cannot, without specific authorization, exercise the right of ownership in time sharing.