Stepkids vs. Kids

I read a lot of contradicting things here..

So I'm looking for a bit of clarity..

I read a lot of : you should treat stepkids like your own.

But you can't discipline them like they're your own.

And your rules don't matter like they're your own because only their mom and dad rules count.

If you both have kids from previous relationships, all kids should be treated thesame.

Yet you have your own strategy and your ex might have their own and you and your new partner might think alike but his ex has a different strategy.. Which means that you have to compromise with your ex and new partner had to compromise with his ex which ultimately comes down to the kids having different rules.. Right? Because the other parent matters and they legally have a say in how their kids are raised.

So I feel all of this is kind of contradicting...

Because it's impossible to treat a kid as your own while literally being told that you're not supposed to treat them like your own. Even when you do love them thesame.