The kids are more annoying to me by far.
Pets are unpredictable, and usually when people post pet stuff it's because they did something entertaining, silly generally out of the ordinary. Sometimes these are actually entertaining and/or amusing.
When parents post stuff about their kids it's usually the same old boring milestones that ALL kids get to at some point. So your kid took a step. So did every other kid who came before them, and so will every other kid who follows. Not exactly a grand achievement, so who the hell cares? The answer is "your family and friends care" - that's true, so please keep it in your inner circle of those who give a shiz.