I will admit that it is much easier to find fault with other kids as opposed to my own. Parents seem to have blinders for the aggravating and just plain awful behavior of their own kids. I realize this and sometimes check myself. Like, if SO's kid is doing something that really gets to me, i ask myself if one of mine has done this and how i felt. Or, if one of my kids does something mildly aggravating (to me), i ask myself how i would react if it were someome else's. It helps me to be more fair in my actions and words. Sometimes, however, one of his kids will do something that's just completely awful and i can rest assured that mine would never act so badly! It sounds like you have raised yours to be well-behaved and considerate. That is a good feeling to have! 

NOW SD21 was my problem and I didn't think we would ever, ever be close. Her behavior was atrocious.  And I'm pleased to say

she's grown into a lovely awesome young woman and I like her.  The one I was super close with originally grew up to be a sex worker and became a BPD narcissist.  You never know.  I advised the both of them throughout the years.  One listened and one didn't.  

I'm a mom to four and yes sometimes mine can be horrible little brats!  I think you actually have to parent and hopefully you will see results.  Sometimes though you are fighting an uphill battle. 

I think what happens is that people raise their kids with their own values. You see your kids displaying the values that you taught them and it's positive. BM and your DH have a different set of values and they have raised their kids accordingly so it's easy to not approve of somebody who has an entirely different value set than you and your kids. 

This is why step kids are so easy to hate and they seem so foreign to us. If you had raised them they would have cared about what you care about but they don't. 

Many times, I was exasperated by something one of my SK did.  Then my own bios did things thst would make me silently cringe but DH took it all in stride.  We just view other people's kids differently.

I was talking with a friend and former co worker yesterday. Her oldest DS who is young is very strong willed and she was upset yesterday because of how she feels she has to constantly redirect him and why will he not just ever listen.

I told her how DS from ages 6-10 was the same way and how I literally felt like I spent all those years disciplining him. How I was also embarrassed at times and frustrated. But that with structure and consistency as he matured everything changed and parenting got easier.

All kids have periods were they are difficult that's to be expected. The difference in stepworld is that often you are dealing with hostile, possibly emotionally abusive BP who sabatoges anything OP may attempt to do. Guilty, Disney catering BP who lacks a spine. 

Which is a recipe for creating children who have emotional and behavioral issues. As well as no respect for authority.

I actually have a video I keep as a reminder of the insane level of ridiculousness of SDs behavior. YSD 13 was making scrambled eggs, she burned them. Her response was to completely lose her shit and engage in a tantrum, verbal tirade for over 10 minutes that would have made Linda Blair proud. I'm not kidding when you would have thought the girl was possessed.

Unless you've got a real difficult child. e.g with serious mental issues, it pretty much comes down to parenting. I've since realised that coming here I don't dislike my skids, I dislike and resent my partner who does not deal or discpline them. Granted discipline them like I would want them disciplined but I am firm but fair. There is something more going on with her, guilt because of divorce or guilt because of something else or just lazyness and a desire to avoid hassle. I couldn't tell you which.

While I recognize the propencity that a bio parent may have to favor their own progeny over a Skid.... when the comparison between BKs and SKids is boiled down to behaviors, there can be a true comparison.

Kid behaviors have a direct relationship to effective parenting.

Feral Forger SD22 is really that bad. Stealing. Lies. Rude. Dirty. Lazy.

Her sister, SD15, by comparison, shes been pretty ok, with exception of school-gate. Ive treated her like my own bio in the past, and objectively speaking shes way better than her sister. And I have no bios of my own, so I have to use that as my example.