Should I stay or go ?

[Trillhouse]

Little info first.
It's been 5 years together (they say it takes 5 to 7 years to blend). My partner has two childern from previous relationship 10 and 8, we have a 4 year old and a baby together.
Since the beginning there has been problems with the 10 year old SD. Without going into too many details, we (including her bio mother) are concerned about her behaviors (lying, stealing, manipulation, lack of Empathy, cold callousness, narcissism etc).
I don't have to tell you alot of her coldness etc has been directed at me including the stealing.

This in and of itself has had my alarm bells ringing saying run run run but stayed and we have two wonderful childern together.
Beside the resentment I feel dealing with my problematic SD, I also feel like a second thought to my partner.
I'm on maternity leave and doing online school while he works Monday to Friday. Even than i get very little help when he comes home from work. Than we have the step kids Thursday to sunday, which feels like stress and tension the moment they walk in till they leave for me.
Now they have sports practices Monday and Tuesday, so my partner eats dinner with us than leaves to watch them practice, not games practice.
So the 3 days out of the week that I had to be with him without the step kids around is shorten to 1 day.
I feel like the family I made with him is less important, like if it comes to our kids having a sport practice etc he wouldn't prioritize it the same way he does with the step kids.
Our connection is fading as we get no time alone together.
And the SD thing has caused so much stress among both of us, it's come to the point that I don't even like the kid at all. Her personality etc, I don't want to even be near her. I love and care for my step son, but she sucks all happiness and calm out of every room she is in. My friend recently told me, that when she was little her husband wouldn't come out for coffee if she was there, cause "something is wrong with that girl".
If anyone has been in this situation, please let me know what you did? Should i stay or leave. Also how is it separating when you have kids with the partner that has step kids.
Cause if I did leave I don't want my kids visiting him when she is there and I don't know if I can control that?
Thanks

My exSC were very mean to me but I guess they were young and very influenced by their own DM. When I had my own DC, there was no way I would let them babysit - they were only v early teens. They thought this most unreasonable. I didn't give 2 fks. They both have young DC of their own now and I hope they can understand, heck, maybe one day they'll even be step-parents.

I split with my ex for other reasons but the step kids and his ex didn't help. If everything else is ok then ride it out?

I would be tempted to leave with your DC and stay at your parents one weekend a month, it gives you breathing space from the stress and I’d time it to be a weekend his children stay. You need time away and so does your DC, it sounds very stressful and it would be good for you to step back away from the situation. Your SD is clearly a very troubled girl and sounds like she needs counselling, all the attention is going on her, her brother doesn’t get a look in, never mind you and your DC.

That doesn't sound like a happy life. I'd be out the door I'm afraid. Not sure why you had two kids with him within such a short time of knowing him though.

Re the problematic step daughter can you get cameras up? That may fix bad behaviour instantly. If you want to stay in the relationship could you speak to your partner about couples counselling? You really need to be united imho for these blended situations to work, although ups and downs are par for the course. The book strpmonster is brilliant if you havent read it. Strongly recommend reading it and getting your other half to read it too.