DSS16 living like a hermit and DH seems to be in denial

Your DH is a crappy parent.
Whats your relationship with his mum like? (The ex I mean not your Mil!)
I agree with you it’s concerning and it’s not healthy… how close is your relationship with your step son? You could offer to host him mates or similar. When he’s there at yours, you could do things like go to the cinema / out for dinner with him & DH, does that ever happen?
You could also have broken internet one weekend that he’s there and see what else he does to entertain himself….
Your DH is not engaging much by the sound of it and I agree with you/ can see why you are concerned. (Ialso wondered if he is smoking weed? Don’t ever let that happen or it’s game over)

'He feels like he’s doing a grand job as he’s always had him every weekend and half of every school holiday'

How do YOU feel about his parenting though, because im getting the impression this isnt the first time he has insinuated he's a spectacular dad because he does the bare minimum, has he always been one to shy away from the hard bits?

Could you gently suggest to DH that he at least eats dinner with the 2 of you?

Also, does the son actually want to learn to drive or is this DH just being hopeful/delusional?

He is 16, so what happens during the week. Is he at school or college? Maybe he is finding the situation there very stressful and the weekend is when he decompresses. I would want to know about the rest of his week before I started to worry.

What kind of relationship do you, or did you have, with him? Could you have a quiet conversation with him and ask how he’s doing, if he has any worries and if there’s anything you can do to help?

What is your relationship like with his mum? Could you speak to her?

Poor child. Has been failed and still being failed. There must be hundreds of thousands of kids like these, what hope do they have of becoming a functioning adult. It’s very sad and completely the fault of the parents.

Do you know anything about how DSS lives when with his mum?

this is really a DH problem. He should be engaging with his son, joining him in the gaming, encouraging him to eat family meals and be less isolated. You can’t fix this unfortunately.

It sounds extremely worrying but you can’t do anything about it, which is very sad. As a step parent no one ever thanks you for caring more than the parent does, you’ll be trying to push water uphill even trying to change the dynamic. What’s he like at his mum’s? Does she know what’s happening when he’s with you? It can’t have always been like this, when did it start and what precipitated it?

My son is like this but he has autism and struggles with the outside world.

Leave to DH it's not your son

I wouldn't accept it as a parent but you arent.