Castleford dialect

These are just dialectal remnants of past English forms or derivations thereof. See the example for 'hers' below and the rest will fall in line for you. From the online etymology dictionary:

hers
c.1300, hires, from her; a double possessive.
Possessive pronouns in Modern English consist of the predicative (mine, thine, his, ours, yours, theirs) that come after the subject, and the attributive (my, thy, his, her, our, your, their) that come before it. In O.E. and early M.E., they were identical. To keep speech fluid, speakers began to affix an -n to the end of my and thy before words that began with vowels. This began late 13c. in the north of England, and by 1500 was standard. Then the predicative and attributive pronouns split, and the pronouns in that class usually took up -s, the regular affix of possession. But the non-standard speech of the Midlands and south of England extended -n throughout (hisn, hern, yourn), a habit attested from 14c. and more regular than the standard speech, which mixes -s and -n.