I have troubles finding a rule (if there is any) regarding the declination of adjectives in Dativ, and the suffixes that they get.
I know that the articles will switch from der-die-das-die to dem-der-dem-den, or from ein-eine-ein to einem-einer-einem, but I'm not sure what happens with nouns and adjectives.
For example, let's say that we're talking about "mein alter Vater" or "meine alte Mutter". If I want to say that I'm coming with one of them, that would be "Ich komme mit meinem alten Vater", or "...meiner alten Mutter".
Is it a rule that the the article (or possessive pronoun in this case) always gets the "m-r-m-n" suffix, and the adjective gets the "-(e)n"? Could it happen in some case (with certain adjectives) that I can say "...mit mein altem Vater / meine alter Mutter"? What is the rule? Are there any exceptions? Or should I say - is there a rule about exceptions?