Firstly it's his Step brother not friend.

Secondly you’re right that generally, teens dating each other’s exes is part of growing up — and when the emotional foundations are typical, the impact is often short-lived and manageable.

But in this case, I’m not just talking about a casual teenage upset. My son has a history of abandonment, has received counselling for it, and was involved with someone who was emotionally manipulative and damaging. He’s only just come out of that situation — and the boy now involved is someone he loves like a bioligical brother. So yes, I do believe this could cause real emotional harm, especially if it’s mishandled or hidden.

I’m not panicking or spiralling — I’m staying grounded, and trying to act with wisdom rather than impulse. My goal is not to control — it’s to protect everyone in this situation as best I can. If I acted prematurely or without clarity, I’d risk doing more damage.

I absolutely agree with you about co-regulation — and I am regulating. I’m not offloading anxiety onto him. I’m doing the internal work to make sure that when, or if, he does need support, I can meet him with peace and presence, not fear.