Pennsylvania, like most other states in the U.S. consider pets as personal property. When a couple goes through the divorce property, a pet is considered property much like a vehicle, a painting, or even a coin collection. It is up for grabs in equitable distribution. Sometimes, for couples with children who are especially attached to the pet as well, the couples will agree that the pet will live with the primary custodian of the children, because it is in the child's best interest to have the pet around them. Or maybe the couple shares the pet, so the pet goes to the house where the children are currently at. Anything can be negotiated, but if both parties are fighting over the pooch, no custody statute is applied.
However, some states have enacted pet custody statutes to help out with this problem, and it seems to be a growing trend across the U.S. For example, Alaska became the first state to allow judges to prove for the "well-being" of pets in divorce actions. The Governor of Alaska signed the bill into law in October of 2016 and became effective in 2017. Alaska's law gives the Judge the authority to go beyond the traditional property paradigm for pets when dividing marital property.
Illinois has also followed Alaska with a similar statute of their own where the Court should consider the "well-being" of the companion animal, but notes that "companion animal" should not be extended to "service animal," because that is the sole property of the person who needs and registers the "service animal."
With the above noted states allowing a more extensive review of the "well-being" of the pet, Pennsylvania is still a state that considers animals/pets as personal property. But who knows, with service animals and emotion support animals growing at an unprecedented rate, more states may start introducing bills that follow more of a custody statute analysis rather than a personal property analysis.