It totally depends on the mood, and how things are going, lol. When shes bad, shes "his child", when shes good shes "our child". 

But seriously it really does depend. If you are involved heavily or disengaged.

I refer to SO's kids as his.  I don't want any part of them being 'ours' - morally or financially.

But his kids were all over 18 when we met.  I have zero relationship with his older two and I am disengaged from his youngest (Bratty McBratFace, who turns 24 next week).  So it would be bizarre to suddenly refer to them as ours.

"His" kid always. When we were childless, people would ask if we had kids or not. I would say "___ does from a previous marriage." Or vice versa. 

I have no say when it comes to instilling morals or values, so no, I would not claim as "ours".

Like above it really depends. I often say "our" and refer to SS as my son most of the time because BM is not in the picture much and SS gets hurt if I don't claim him. He's a good kid now so I don't mind. Back when he was being the child from the devil it was 100% "his son" or stepson. However, SS is only about 15 years younger than me (and I look a little young for my age) so I usually get a really odd look from people when I do say our/my and end up having to explain I'm actually the stepmom.

also, ss usually says "my parents" and refers to me as his mom or stepmom when talking to others. Day to day tho in our conversations he mostly calls me by my name.

DH says his daughter, because that's what she is, she is not mine. She has a mom and I'm not it.

I am bioless full time "stepmom." I've been with SO going on 6 years and I never once said my "step kids" because they aren't because we are not married. They are my boyfriend's kids. SO would never say "our" kids. To me that's weird. 
 

NOW skids.. SS16 says "my parents" when talking to friends about SO and I. Pretty sure SS17 does too. SD14 will say dad and missk. If SO and I get married then SD might say stepmom when talking about me not sure..

I have noticed that we say things to others like "the 4 kids between us" or "our combined 4". At home there is the occasional "your kid" or "my kid" but I feel like we both take parental responsibility of eachother's kids.

I am childless - I met my sk when they were adults / late teenagers.  They are his kids.  They have a mother, etc.  However,  that said we all are somehow stitched together in a very loose unconventional family thing - and it works.  But, regardless, I am "dad's wife" and I am happy with that.   I suppose it might be more complicated if the sk's are young and you are working away at helping raise them.  However,  with this modern blended thing - at the end of the day -- the parents are the parents - and the kids are their's.  It's  complicated. 

I don't have kids.  I met the SSs when they were all in primary school, so farily young.  But I've been disengaged from day 1 for the most part until YSS had to move in with us full time from late teens until launch.  The only remotely parenting thing I've done is tutor YSS and MSS in French to improve their accents but even that could have been outsourced to the 3rd party by the parents.  And I only did it because each SS asked me for help themselves.