Do I tell them about baby no 3

Me and partner have been together 3 years. I have a 7 year old daughter from a previous relationship who he is just the best stepdad to. We've recently had a baby boy together in Jan this year. Everything was fine I'd say until our boy was born. Backstory is in 2016 I lost a daughter and 32 weeks due to preeclampsia, I stayed 5 days in hospital with my stillborn baby in a cold cot and then later buried her. Fast forward to post partum with my boy and the mum and sister of my partner start doing little things like trying to feed him in the very first few days and texting every day to come see him. Obviously I was very sensitive to having my new baby and previous trauma arose. It took me a while to get in to the school routine of taking baby along and just generally finding my feet, his mother messaged saying why are you stopping us from seeing the baby. Every time she wanted to see him I would be busy so would give an alternative but she'd not reply. I then get diagnosed with post natal depression/anxiety which when they turn up announced outside wanting to come in I sent a text back simply saying could they come when my partner was here in the evenings so they could see us all including my daughter and not just the baby. In which hell broke loose, the sister completely attacked me via WhatsApp calling me vindictive and a bitch and disrespecting the mum. Then brought up things that she knew about my previous relationship. Insult after insult. There has been so much stuff that was said by her but soo long. Anyway suffice to say I went no contact with them which my partner supported. We haven't spoken in 10 months until the sister turns up unexpectedly wanting to apologise. I let her in as I was sort of blindsided. I let her say her peace but got called controlling (apparently controlling her brother) in the process. Fast forward to now we're 8 weeks pregnant I don't like any of them and couldn't care if they were in my child's life or not however do we tell them we're expecting? Thanks for reading