Some pets are downright finicky about everything: food, bed, and even particular spots in the house where they elect to groom.  They might be sweet to you, but you may be surprised to uncover a streak of jealousy in them.

It's not unusual for cats and dogs to express their anxieties over a new person in the household by seeming to forget that they're housetrained. Cats have a reputation for urinating on thier owner's belongings, and dogs may find a new place to mark as their comfort zone. This is not spiteful; rather it is a stress response and should be treated by giving your pet more things to make them comfortable, while firmly reinforcing the rules.

When people experience issues with their dogs because of a relationship, the troublemaker is often a dog who is accustomed to being the center of attention, constantly petted, and given frequent treats. These dogs may act out when they are forced to share their human. They may jump inbetween their human and the new person or bark, growl, and block the new partner from the bedroom.

Cats may tend to hide when they don't like a person. They may run away, if they are really put off by the new match, but this is unlikely if they are given reassurances. Cats might snub the newcomer for some time, and could act aggressively by hissing, spitting, and possibly clawing or nipping.

If you find yourself in a standoff with your partner's pet, talk to your partner and arrange to be the good guy for several weeks - maybe even a few months. Deliver treats, favorite routines, feed the pet regularly if living together, and take the animal for walks. If they are afraid and tempted to run, try tossing some treats their way before you get too close.