Why are my dogs so misbehaved?

i put more effort into my two dogs than myself... i think i take care of them very well.. they are two labradors one is one and the other is about 6 mo's old... they chew everything when im not home and when i bring them to my parents house they go crazy... I have done everything and i feel hopeless! my parents adopted their dog lucky and since day one never had to train him and he is so obediant and such a good dog.. what is the problem?