Regular but NC. I've posted about SIL before but in short: DP is a middle child, always felt hard done by, he gets treated worst but he was always close to sister.
We both hate SIL's husband (DP's sister and his BIL) he's a horrid man. I wish I could tell you the reasons/scenarios but way too telling. Just think of someone who wouldn't respect you if you earn too little and thinks nurses are a waste of space and too dumb to be doctors. Genuinely.
DP has had some issues rising with SIL since she got married as she has changed. She's become less fun, more uptight, and a bit of a dick tbh. Everything came to a bit of a heat when she organised a Christmas gathering and invited everyone in their immediate family except for us.
DP decided to confront her and they had a pretty matter of fact but upsetting disagreement on the phone. She was very defensive and in DP's defence he was just factual. The husband then sent DP a message that was very rude and said that she's already struggling as a new mum and that "maybe you would understand if you ever have kids".
I thought it was out of order for the husband to get involved. However, now he has I am wondering if I should talk to SIL? I'm quite good at saying the right thing and want to help her realise why he's upset without the emotion as the third party.
Is this stupid? Where would you go from here?