To be furious at partners mum giving his dad updates on DS?

[etceteras]

DP is NC with his dad as he was abusive during his childhood. His dad has tried getting in contact and apologising but DP doesn't want anything to do with him. We didn't think he knew about DS (now 8 months) until the other day when his dad messaged him on Facebook asking if he could see his grandson, we were confused as to how he found out and DP was talking to his mum about it and she admitted she’d be sending updates and photos to his dad as apparently he deserves to know about his grandchild.

Am I BU to be furious or am I over reacting?

Your mil sounds like she's in the middle here. I wouldn't be furious at her

Maybe have a conversation of the boundaries you have as a couple and what you are and are not at happy at sharing

Stop sending her updates.

Are your DP's parents together? If so, yes you were unreasonable to not expect her to share things with her husband. If they are separated could there be an issue of coercive control?

We don't always send her updates, she sees DS often though. And they're separated.

What’s dp’s mum’s relationship with her ex generally? If amicable and they’re in touch, then I guess I wouldn’t be surprised she has told him about your dc. Also, have you actually mentioned to her that you didn’t want the dp’s dad knowing about dc?