I (30f) didn’t tell my ex (31m) that I gave birth to his biological kids (twins) and he’s now annoyed at me

Tldr; he has just discovered this now and he’s messaging me asking me why I didn’t tell him and he’s wanting to meet my kids but I don’t want him involved in their lives.

When I got pregnant we were at a bad point and he had broken off with me because he thought I was cheating with my guy best friend, I wasn’t we knew each other since we were kids and there was no romance and my husband (not ex, my current husband) is fine with me seeing him still and let’s me talk to who I want. My ex was controlling and accused me of cheating after I stayed over at his place. I admitted that that was wrong and learned from my mistake that it looked bad to him and said I wouldn’t do that ever again but my ex still split from me.

I found out I was pregnant shortly after, contacted my ex and he told me that he wasn’t going to come back to me and “it’s not mine ask one of your other boyfriends”. I then blocked his Facebook and cut contact completely as he wanted no responsibility and just told me he knew I would get an ab***ion which is what he thought I’d done but I didn’t. I moved to a different place with my best friend and her boyfriend far away from him and started fresh. We all put money together to buy a 2 bedroom apartment and we lived like that for a while until I saved up money and we went separate ways but they helped me so much in getting stable and they’ve gotten married now and my daughter was a little bridesmaid at their wedding.

Anyways, I met a new man who I’ve fallen in love with and we are now married and I’m currently pregnant again. He’s the emotional father of my kids and he is their dad even if not biological. They call him dad and he is their dad in a way. He’s raised them and loved them as his own.

Now, my boyfriend’s mom has (don’t ask me why) looked at my Instagram. She was nosey so maybe but it’s odd she’s done that after so long, maybe because he’s single and she’s thinking of his exes? And she saw that I had 2 kids the right age that do look a bit like him, they both look like him especially my son. But she brought it up to him I think and he’s now messaged me on Instagram asking if they are his which surprised me. I told him they were and he didn’t reply for a while until he then sent me a massive text saying that it’s unfair I made him miss out on so many years with his kids and that he wants to see them. I explained that they already have a dad and that they won’t know him. We also online a long time away and I don’t want to disrupt my kids lives like that because they’re going to highschool soon and I want them to settle well.

His mom and other family are now harassing my social media and I’m not sure on the best course. Maybe let him meet them? I don’t want to send them away with a stranger now. Maybe he’s changed but I still don’t want him in their lives as he’s a complete stranger and even though he’s biologically their father he’s not their emotional father. I’m not sure on the right thing to do.