Raamaayan seems to have some bearing on number 12. 

It has 6 Kaand, which is half of 12.

The total number of verses are 24,000, which is double the number 12,000.

Vishwaamitra's coming to Dashrath and Seetaa's marriage is also in His 12th year. (Maareech said this to Raavan, but Dashrath said less than 16 years).

His stay in Ayodhyaa, before His Crown prince ceremony and exile was also 12 years.

Raam's exile period (Vanvaas or forest tracking) is also for 12 years plus 2 years in Panchvatee.

Raam killed 12 great army chiefs of Khar in Jansthaan.

In Uttar Raamaayan, Seetaa stayed in Vaalmeeki's Aashram for 12 years,

Raam Himself had not attained all the16 phases so He was not a Full Avataar of Shree Vishnu.

Some events are connected to 14

Kaikeyee asked Dashrath 14-year exile for Raam.

First Raam killed 14 Raakshas sent by Khar in Jansthaan,

Then He killed 14,000 Raakshas in Jansthaan 

Grouping of Verses in 24 books in Ancient Raamaayan

The whole of Raamaayan consists of 24,000 verses and Gaayatri hymn also has 24 letters, so each book of Raamaayan contains a thousand verses, starting with each letter of Gayatri hymn. This is the then classification of the Adhyaay (Kaand) of this epic and such grouping of verses is nonexistent now.