You don’t have to pay “child” support on behalf of pets... at least not yet and not for 18-21 years.
I know a childless couple who battled over their dog in divorce court. The judge divided custody. The dog traded homes every other week.
More importantly, pets involve a much shorter commitment than children; “pet parents” usually have much more turnover due to the shorter lifespans, so they have numerous opportunities to opt out (unlike the lifelong commitment to children, grandchildren, etc.).