What's with my dogs behaviors ?

i have 2 chihuahuas a male and a female my male chihuahua always follows the female and he always copies her if she drinks he drinks if she eats he eats if she plays he plays he follows er everywhere well you get the point and i gave my dogs each a chewing bone and when they each have one my male dog tries to take my females bone that she's chewing on and that kind of breaks out into a fight sometimes. hes more boring then her also and they're not even old dogs. barely a year old. he's lazy alot and sleeps all day .and they're always chewing on each others necks and chasing each other i can't tell weather they are fighting or just playing? they don't growl they just bite each other but not enough to pinch through the skin its not harmful bites and they dn't wimper either they just chew on eachother all day . but i just wanna make sure if they are just playing or if they're just annoyed of eachother . but when i separate them sometimes they always wimper for each other so i dont get it its like a love hate relationship between them ?