See, I actually liked my SS more at that age. He was my little buddy and we had a lot of fun together. He was moldable and respectful and actually liked us, so we were still able to influence him, even with our limited long distance visitation. 

Now my SS is 10, and much like you describe, I can't stand him. He is entitled, rude, and disrespectful. He is honestly a mini BM - always having to be the best at everything, being a constant know-it-all, being set in his ways and less willing to change, and constantly arguing with us about everything. Everything is "my Mom doesn't do it that way or BM this or BM that." DH has to constantly remind him "our house, our rules," to which SS argues. I'm sure it is a personality clash, since BM is raising him with different values, and I'm sure part of it is me not caring to hear about BM all the time. I honestly wish I could say it gets better. 

SD was fine until about 9, that's when she learned to start being manipulative. It's the age where bullying and cliquey mean girl behavior starts. She wasn't a nice kid anymore.

If even when she’s being sweet, you can’t stand your 4-year old SD because you feel she’s being manipulative, then the problem is not the SD.

Good luck.

While 4 can be an annoying age anyway,  it's also possible that she is already spoiled. 

What kind of behavior are you seeing? 

from the very beginning, so about 5 or 6yo. She was not cute, she was mean, and she liked to divide people.

BUT I gave her the benefit of the doubt, and I included her in everything, tried to show her what a real family was like. That we didn't have to FIGHT for attention, that we didn't have to TURN people against each other to get them to like you.

NONE of it worked, 11 years later, I STILL can't stand her, she's even WORSE than before, as her actions were from a 5 and 6 year old, and were very obvious. NOW that she's almost an adult, she's perfected her skill, and only those who REALLY know her can see what she's doing...

THANKFULLY karma has cought up and she has no more friends due to her actions. She's going into senior year with EVERYONE at that school knowing what kind of person she is (she did all the above to all the popular kids). TOO funny imo! Everyone in my house knows exactly what she's about, and don't trust her. My kid's are kind though and are being nice to her... but they are still guarded with her.

Eleven for one and 13 for the other. They've always been a bit obnoxious and entitled, but I assumed it was an age thing (met them when they were 9). When they not only didn't mature at all, but only became worse (one had screaming, crying, tantrums on every visit, the other one is a total antisocial weirdo).

Though I have disliked some of his behaviors periodically and it did take some personal adjustment to have him in my life. Usually that was related to pre-visitation behavioral degradation and post visitation behavioral detox. About 7-10 days prior to departure for hte former, and 2-3wks after return from visitation for the later.

I knew his mom was the one and to make that happen I had to accept and raise him as my own. That epiphany did not take more than a few weeks to adjust to once his mom and I started dating.  From that point, we have been the three musketeers for the most part.  I love my kid very much. I raised him as my own from before he turned 2yo. He asked me to adopt him when he was 22. We made that happen. I am a proud dad.

We really had little problem with him other than some fairly not unusual teen boy brainfart-itis.  We dealt with some of that with Military boarding school his Jr. and Sr. years of HS.  Though we did cut that short by one semester when the Spermidiot helped him hack the school firewall and they stayed up all night nearly every night playing WoW.  Resulting in SS failing the only Fall semester of Sr. year class he needed to graduate.  To keep him there to make that class up would have cost us another two semesters of tuition as that class was not available in the Spring or over the summer and he could not take the follow on class for Spring without passing the Fall class. So, he came home at Christmas break and had to bust his ass at our local HS to graduate on time.  Which he did, and with honors. Though he was one miserable young man with his very disappointed mom's hairy eyeball on him 24/7 until he graduated.

He only needed one class during each semester of Sr. year to graduate at the Military School.  At our local HS he needed those same two classes plus an extra math class, two career path classes. He built a computerized music inventory system for the school as his career track credits, and he had to complete a Sr. project that usually took from Mid year of Jr. year until Spring break of Sr. year to finish.  SS had 7wks to complete that 15mo project.

This was a huge learning experience for SS and he did learn that choises and failure to perform to standard both have consequences.

For the sake of full disclosure, I also attended Military boarding school to keep me focused, as did my dad, and my younger brother.  SS had the opportunity for that family tradition as well.

He has done well as an adult and his mom and I are, as are his Rags clan family members, very proud of him.

Honestly it wasn't her I didn't like it was the situation.  She was basically dumped on us less than a week after we got married.  I think I started to dislike her about 9 when she would blatenly lie and DH would believe everything she said.  She was doing inappropriate things and no one saw fit to do anything about it.  So I think it was about then I started to sort of despise her and the situation.  But I digress- I will say the lack of parenting in her lift has caused MAJOR problems as she enters teenhood. 

My exSD was 20 when I met her.

I was friendly and polite for our first few interactions but it got me nowhere.

I've come to realise that she would not have been someone whose company I would seek out, no matter whose kid she was.

She is basically not a nice person, sadly.

i met exSS when he was 4.  he was ok toward me but still spoiled,, it just got so much worse after that and ended up driving a huge wedge between myself and his father ,, too much of a wedge that i had to call it quits when the kid was 12.  DH spoiled the brat so much and turned a blind eye to everything the brat was doing.  I had no say in anything.  In the end i couldnt be at the butt of the kids anger and dismissed by DH aymore , it was horrible!     4 yr olds are annoying and i dont doubt that its going to get much worser as she gets older