divided between stepchildren and baby

My dsd was older than you are talking about but I made it clear that i wasn’t her mum, but i was there for her and she could talk to me about anything (including moaning about her mum). This approach that I’m a friend not an authority figure worked but she was already a bit older, not that much though. She didn’t get a free ride from me, I made my expectations clear that house rules for her were the same as my dd, I’m not a soft touch!

you need to find the middle ground that works for you

Despite being a fairly new joiner to MN, I have seen a surprising amount of similar threads from young women who chose to get into relationships with older men by 10+ years and how they have struggled to adapt to role of SM and have ended up doing the brunt of childcare for their joint and SC without really having had a chance to learn the ropes as it were.

OP sounds very mature and I’ve no doubt she can make this work with the right advice and guidance but I’m glad she and others in similar scenarios post because any other women in their early 20s can read this and make informed decisions about what life actually could feasibly be like and whether they’re prepared for it if at anytime there was the potential to date significantly older men with fully formed families already.

Why are you being so weird about ages. You are the one who keeps insisting late teens and now you are criticising others for correcting you.

OP is just 30. She said she would have been 16 & 14 if they were her dcs.
so the sdc must be 14&16. That’s very clearly early and mid teens.

no one is a late teen

14 & 16 year olds need parenting. School can be really tough at this age. Hormones are crazy.

@MaggiesShadowthe DSc are not late teens they are early -mid teens. Still quite bit of parenting required

What your husband wants might not be very realistic. Teens may or may not be interested in the baby. But forcing contact like forced babysitting is going to cause resentment if they don't want that contact.

Having to watch your younger sibs can be a form of parentification and it's not a healthy dynamic and again, can cause resentment.

You want honey, not vinegar here.

I agree with this.

Don’t be their parent. If she wants to go out without having done her homework, remind her that her dad wants her to do her homework before she goes out. If she chooses to go, it’s up to him to deal with that. If she won’t tell you where she is going, tell her she needs to text her dad and tell him. If she refuses to do that, it’s on him to sort it out with her.

Make it clear to all you will remind them of his rules but it isn’t your place to enforce them.

I feel sorry for you because it must be really difficult to deal with these dynamics and all of the upheaval of becoming a mum.

Ultimately though, the children in any family come first and 2 of the 3 have had an incredibly challenging 4 years.

I'm sure they will love their baby sibling, but it is absolutely to be expected that they will struggle with a new addition who is both yours and their dad's biological child and lives in your home full time. Especially since it's only been 4 years since their parents split up.

I think you need to be quite sensitive to the mix of emotions they are likely to be feeling. I wouldn't ask them to help at all with the baby for your benefit, they didn't create the child and it's not their responsibility, but welcome their involvement (where appropriate) if they want to do things. There dad should be going out of his way to reassure them that their place in the family hasn't changed, even if that means taking them to age appropriate things alone. And whilst their dad should be reminding them about being polite etc., I'd give them a hell of a lot more leeway if they act out at the moment.

You don't need to be there parent, just a kind and loving adult in their life.

Is there a chance your DH is putting too much of the parenting of his teens on to you?

I'm no expert in this but they have a mother and a father, do you need to mother them too? Can't you have more an an Aunty type relationship?

I think you should approach as you are another consistent adult in the children life and let the parents do their job.

Whilst there are some people do have children young most people do not become parents at 14. The OP is not a typical age to have teenagers, especially step-children as teenagers.

If they’re receptive to it, it’s fine. There’s no hard and fast rule.

You are overthinking OP, just take a step back. Relax a bit. Having a new baby isn’t the time to suddenly start worrying about everyone around you. Be pleasant, be courteous and respectful.

Women too often start making other people’s problems their own and taking everyone’s burdens in the household. They aren’t all yours.

And unfortunately not all children see their half siblings as siblings. I didn’t and unfortunately my son doesn’t, they were just our parents’ new children. It’s sad and hard but it’s just the way blended families go sometimes, especially when there are very large age gaps.

Most useful thing someone told me is to remember to be kind to myself. Ease those high expectations, enjoy the craziness of motherhood with your little one and let your DH do the heavy lifting with his own children. If things go tits up for step mums it’s normally a DH problem!

With a supportive hands-on DH, you’ll muddle through just fine.

I think you need to create some time to bond with them more. Find something you and SD like doing (shopping, nails, tv show, coffee etc) and something you and SS like doing ( this may be harder but be curious about his interest) - then carve time out to do that.

Also be honest with them that your not trying to replace their mother but you care about them and want to everyone to be comfortable at home.

I agree with PP about trying to not parent them too much at this point as you need to get to know them first

Don't. You are not their parent. Your better off letting DH parent them and building a relationship where your a trusted, reliable and consistent adult and hopefully a friend .

I think that’s totally normal with teenagers to just co-exist in the same space.

Stop parenting them. Enforce rules and boundaries whilst they’re there, but step back and let your DH do all the heavy lifting and address issues of concern.

Pick the biggest issues and figure out, with your DH how to address them.

But take a step back and focus on YOU and your baby. Do not fall into the trap of being fall back parent/lift bitch etc because you’re home.

"Re my SC watching the baby, it’s also that they’re half-siblings"

You're in essence asking them to watch their replacement. You need to avoid acts that can engender or increase resentment. They may have positive feelings about your baby, but there are some negative ones too and pushing artificial closeness, not a good idea. In fact, if there's quite a bit of turmoil, some counseling sessions might be in order just so they have a safe place to express their probably very conflicted feelings.

But why aren’t you engaging with them? You can absolutely be a friendly adult that they live with, converse with them and ask them about their day etc. but if they ask if they can do this, go there, have this etc. just default to dad every time. ‘You’ll have to ask you dad about that, why don’t you give him a call?’

Okay, and has Mum ended up living with the AP? It would appear that the adults in the situation have moved very quickly and this is obviously going to be incredibly difficult for the kids… but what’s done is done.

I think you need to just take a step back from the teens, don’t take on any sort of authority role, they have 2 parents for that. They shouldn’t be asked to help with the new baby either, it’s really not fair and a lot of kids will resent that. I would just talk to your DH and agree that he is the parent, he sets the rules, you’re not happy to enforce any rules, you’re just there to be friendly with the kids and support if they ask. For example, if the daughter goes out without having her homework done, not your problem to correct her, her father can deal with it when he gets home.

They will have moved out in a few years time so I think maintaining some distance will being friendly and supportive is the best course of action really.