Developmental question

[WSM123]

DSS 3yr,5mth old. He doesn't speak at an age appropriate level, you can understand occasional words but its mostly babble and everything begins with "d" Dish for fish, etc. He is only partly toilet trained (mostly because his mother didn't bother until recently) he doesn't seem to interact with kids other than his brother (at park just wants to swing, or climb trees rather than play with others), he doesn't know colours and doesn't ask all the "annoying" questions most pre-schoolers do.
His physical development/coordination etc seems fine but to me he seems cognitively delayed. Am I righto be concerned or should I ignore it? I have mentioned the speech and my partner agreed but was convinced by his ex that he was just shy around us so didn't speak, I tried to point out that he doesn't not talk, he just isn't understandable (like hes stuck at two).
Any advise appreciated

Thank you for you help, I did ask my partner about that but he assured me that's one thing his ex had done was have his hearing checked (which is good but also makes me think she must be aware that at least something isn't quite right so frustrates me that she hasn't had his speech assessed)

WSM it sounds like both mum and dad are generally "happy" with the approach each of them are taking to parenting their DS.

Hard though it is when you care about a DSC, this really is one of those situations which you can only support from the sidelines. You can't influence it, or change their decisions.

I'm often criticised for advising stepparents to detach - but this is one of those situations in which detaching saves your sanity. There are literally thousands of DCs with the same issues, and you have no way of changing their lives. Sadly, your DSC is no different, you can't interfere with the way the parents choose to parent.

The problem here is my partner keeps asking his ex to get him assesses and she refuses. She also refuses to let him take the child for assessment. Then next time a new behaviour crops up she will accuse my partner of causing it either by allowing rough and tumble play or by a cartoon they watched etc and when he suggested these behaviours might be part of the broader picture she just got nasty.
So sorry in this case no he isn't "happy" with her parenting in this instance (he would also prefer the kids go to school, but that's a battle he can't win so has given up)

I can't remember WSM, are you in the UK? Does your DP have PR?

If so, there are things he can do, but it will "rock the boat" - and I understand that is a big step for many NRP as they fear losing all contact.

Not in uk and he only has access/ visitation every second weekend. He has told her he will organise assessment if she won't but I think she knows how difficult that will be on a weekend.

In the UK, it would be possible to apply for a specific issue order - which, given what you have said, is likely to be granted, I would think.

Unfortunately, without the laws to protect DCs in this situation, you may be facing many years of frustration. Hard though it is, detachment may be the only way for you to protect yourself emotionally.

I have contacted some local therapists and we may be able to get a weekend appointment (I should specify I have done this on behalf of my partner because being self employed allows me the time )