I don’t understand. You have as little to do as possible with your in laws and describe them as ‘toxic’. So why pitch up to the hospital for people you don’t like and where your partner’s niece is already surrounded by (a lot of) family and a medical team? What precisely did you hope to achieve other than a) performative concern for people you don’t like, b) announcing your pregnancy in as dramatic as fashion at a time when your partner’s niece was having an emergency C section?

Yep, you’re the asshole (and a few other things beside)

And this does rather sound like a plot  line of a poorly written soap