DiL wants a divorce I’m devastated

The reality is that as a parent, you're not an unbiased observer. What's going on between them is between them as adults. Your best bet is not to get involved. Your son needs a good solicitor and your access to the children needs to be through him.

So sorry for this mess and the pain involved.
I think you should read back to yourself what is written here. It's clear that it's not a healthy relationship and your son would be better out of it so long as he can still see the children.

If he's able, could he go for joint custody? The truth is, if he really is supporting this extended family to this extent, three little ones half-time should be doable.

Poor bloke, and poor you too.
He is absolutely well rid of her.
I hope that things get better for you both soon.

This is one big pickle
Am I presuming she’s much older than your son if she has two sons of working age ? One of her sons stays around the house smoking weed all day and the other is under police investigation what ever made your son marry her, move into this house and bring three young babies into the middle of this awful situation which sounds very unsafe for babies

I agree with others the best you can do is help him get a good solicitor and get out of this very unhealthy house hopefully with his babies who shouldn’t be breathing in cannabis fumes or living with police coming to the house
This isn’t going to be mended over night though Does the GP, health visitors or social workers know about all these undesirable things happening around the children

Your OH is right he should get out now, it sounds like she had 2 children very young then started again mid 30s. He will have to contribute to his children’s maintenance. If there is any property that will get divided too, there is no avoiding that.

Getting a new partner with live in children, is always going to be risky, more so if you marry, problems are common.

My heart bleeds for you and your poor son.

If it’s as bad as you say, he needs a solicitor ASAP, possibly applying for full custody, it would be worth his while getting all available authorities involved for the sake of the children.
However, he’s has made a bad choice of partner and it really is his problem to deal with, hard though it is for you to sit and watch.
I hope it all gets sorted.

Agnurse is correct. With the best will in the world your son has to hold him self together now. He must think of his children and the future for them.

They both sound overwhelmed! Just reading the story is exhausting me.
3 under 5s for a start. No wonder the older kids are going off the rails.
Why did they have 3 DC so close together? (not my business but it sounds reckless)
Could you offer to take the wee ones to give them a break?
If they do break up you will want to be more involved with your DGC.

Young kids hardly ever get separated from their mother, she would have to be proven abusive, a drug addict herself or an alcoholic. It’s very hard for a father to get custody, trying against the odds is likely to make a bad situation worse.

She sounds like a total nightmare. Still, this is your son's mess to sort out. You'd do very well to just be supportive, detached and non-judgemental. After all, they may get back together!

As others have said Granb your son needs to get some legal advice. He's better off out of this relationship and his young children will benefit from having a happier dad.

As Hetty has advised remain "supportive, detached and non-judgemental". When it's all getting too much for you to hold it in, talk to us here on GN.

He needs out of the relationship and joint custody. You will be able to help while the children are with him. It is not ideal but so many families are in this situation so not unusual.
Please don’t offer opinions or say anything to your d-i-l.

Good advice Hetty 58. It is your son's mess to sort out. As Hetty says be supportive, detached and non-judgemental. They could get back together or not. Keep on good terms with her as you will want to see your grand-children. It is a fine line but if you think of you and your grand-children you can do it. Good luck!

Get a solicitor and evidence. If there are drugs in the house are the younger children safe, doesn't sound safe environment to me. Xxx

This is maybe something your son has not considered. What about him becoming the sole parent of the three youngest children with assistance from you and OH?
It sounds like he might have a good case for taking the children out of their current situation with the older children smoking weed and being under police investigation.
He would likely have to either leave work or work a lot less hours but it does not sound like his current life is very good. He would be doing the youngest children a great service by taking them away from weed smoking and whatever crime the other older child is being investigated for.

Granb3 I am heartbroken for you. My son is in the same position. It is absolute agony. I can't advise but know you are not alone.

Good advice here from many, especially from Hetty58. The relationship between your son and his wife could well stagger on so keep as calm and non judgmental as you can.

You don't say what led to the police investigation into one of his older step children. Police will be mindful of any safeguarding issues if they are visiting the house. One adult smoking weed won't ring alarm bells for the police unless it involves everyone, multi drug use and neglect of the three young children. That doesn't sound the case from the OP

It is do hard when you see your adult children getting hurt and can't do anything to prevent it. What you can do is help your son get a good solicitor and fight for good access to his children. Would the mother be able to cope with 3 babies without your son there? If not he could go for joint custody but only if he could care for the babies half of the time on his own. The situation does sound bad and for your son's own mental health it sounds like he should separate from this partner. Is his partner depressed do you think? If so he could encourage her to seek medical help.

If your son took on the 3 babies he could still work but claim UNiversal Credit and get help with childcare. I know a person, a single Mum who works full time in a demanding job and claims UC and pays a part time nanny who also takes 1 child to school and one to nursery and collects from nursery and school and then looks after children until she gets home each weekday. The part time nanny is claimed for under childcare. The CAB would be able to advise your son about this and what he might be entitled to, you could go with him and make notes.

Granb3-Please look into finding your son some mental health help if you are able to get him to talk to his Dr or see if you have any mental health charities that do counseling.
With most mental health charities you don't need to make an appointment via your Dr.
Some places will even try to help the family as well as it can be hard having someone within the family with mental health issues. (by family I mean you and your husband.)
Whatever he does I wish him luck.

Why would your son choose to produce 3 young children in quick concession with a woman who has brought up her 2 older children to be lazy, a drug addict, disrespectful and a criminal. Did he really think it was going to end well! Very poor judgement on his part and now his mess to sort out.

Its easy to judge as some have done, but love is blind, and things can change and excalate very quickly, especially when the rosy tint of romance has faded a little, that can happen when you have so many children to support!
They are married, he has not abused her in any way, therefore she cannot stop him seeing his children...he must stand strong on this. People forget that while your son might be hurt now, he will move on, and love again, but those children only get one set of real parents...they need him as much as he needs them, and for now, he must put himself second again sadly and concentrate only on making sure those little uns are happy.
He will get through this, in fact it is probably very much for the best as she sounds extremely hard to live with!
If I were you, maybe you could write to her once things are a little calmer, its a bit stormy now, but when its more calm make sure to write to the kids, or send them a card, keep the lines of communication open, don't judge, just support and keep smiling...its all we can do. x

I think that maybe your DiL has issues that even she is not admitting to and really wonder why she married your son in the first place!
First guess would be as either a replacement father for her 2 other sons or just , to put it bluntly, as a meal ticket and I feel so sorry for him.
I have great sympathy for the fact that he single handedly supporting 3 pretty useless adults and 3 babies, plus himself.
He needs to see someone like the CAB in the first instance to find out just what he is entitled to do as far as his own children are concerned , because unless he wants to make himself really ill, I really can see no reason why he would want to stay in half a relationship such as it is.
You job, mum, is to support him in whatever he decides to do - just because she lost contact with her previous partner, no reason to assume that DiL will lose contact with this one - maybe she has family history that you are not aware of that makes her believe that she will be abandoned again ?

I don't understand why he wouldn't be able to see his own children. My son left a similarly bad household situation. The financial and divorce side of it has dragged on for 3 years unfortunately but the access was sorted just before a court hearing a long time ago, and he knows exactly where he stands with his own child. On the negative side, he will lose a fortune, but hew has never once regretted leaving a toxic relationship, and is now with a new partner.