Hi,
I did a it of research here. Latter and former are adjectives but not possessive adjectives. Possessive adjectives are hers, his, theirs, ours, etc.
Former or latter are preceeding some know entity. In the example given, the cinemas.
The latter cinema's names are 'The Great Theatre of Whatever' and 'The Royal Theatre'.
Former's and latter's may be in use, but it is morphed or slang.
I hope this helps,
Stephen