A few weeks have passed since this happened and I'm just reflecting. It's long and complicated so will try and keep it factual.
I co-parent my DC with their dad. All amicable. He lives a few mins away from me and we do things 50/50 with flexibility on both sides.
We both have partners. I don't live with my DP. EXH lives with his partner. Neither me nor ex have gone on to have any more DC and his partner (will call her B for convenience) doesn't have any. She's a nice enough person and adores my kids.
B's sister lives 1.5 hours away and has a very chaotic lifestyle. Sister has 6 kids (aged from 19 to 8). 4 or 5 different dads, none of whom are involved. She's had intense input from Child Services and the younger kids are on a Care Protection Plan. Between them, the kids have a variety of health conditions, behavioural issues and mental health problems (self harm, gender dysphoria). One has suspected autism but has never been diagnosed as mum doesn't take him to appts. The two youngest (8 and 9) display incredibly challenging (often hypersexualised) behaviour and my two DC have found being around them very difficult in the past on visits to where these kids live. My DS has told me he doesn't like going there.
For added context I work in a job that heavily incorporates safeguarding and have good knowledge of how social services operate.
To get to the point. A HV was done by the police a few weeks ago. Police called SS due to the state of the house and the kids were temporarily removed from the house while mum was questioned re: neglect.
B offered to have 5 of the 6 kids come to stay in her and my EX's house. The house is a small 3 bed with the only spare bed being my 13 year old DD's other bunkbed. DS (7) has a tiny box room (so small they had to buy a non-standard bed).
Ex rang me to ask what I thought. I told him that if this went ahead, I'd be keeping our DC at mine until these other kids went back home. Simply put, I had genuine safeguarding concerns for my DC if this were to go ahead not to mention the obvious overcrowding issue. Obviously they didn't need my consent but Ex was on the same page as me - he just didn't want to upset his partner.
They went back to SWs (I even spoke to the main SW on phone - she tried to guilt trip me into agreeing) and said that I had said it was a definite no.
As I had predicted would happen, SS suddenly came up with a new plan and found a house in the kids home area where B could stay with the kids until they went back to their mum (a few days later - house had been cleaned sufficiently for SS to be happy with this).
Ex told me he was relieved that I had said no as he knew B's suggestion was not a good one (albeit an understandable emotional reaction to the situation). He thanked me for being rational and clear.
B is now being super frosty with me. I'm not massively bothered by this as we're not mates and my kids safety will always be something I'm taking zero chances with but I'm just wondering how it looks to an impartial observer.
Biblical length, thanks for reading if you made it this far.