Before anyone says anything, I know it's not my place to say that. But after watching things develop over a number of years, the last week or so has really brought it home to me how damaging he is to her and her DD.
He has temper tantrums where he seems to struggle to control his temper, including clutching DGrandD's hand very tightly (she's nearly 3) to stop her doing something he tells her is naughty. He shouts at her. Yells at her to go to sleep when she is simply lying in her cot talking to herself. This kid is the sweetest, most loving child ever and he is destroying her self confidence. He hates that she won't obey him without question, or testing her boundaries. DD adores him, she is under his spell but treats her like a child. He told her he trusted her to take their own child out for the day. This is such a dangerous relationship and I've spent today in tears thinking about what might be happening behind closed doors. I've tried talking to DD and she just says he is tired and stressed (he stays at home while she works). He had an affair a few months back which he claims was 'just making out', the OW claimed they had full sex. I know which I believe. Then he had an appointment in the week when I was there, he went out an hour earlier than he needed to.
I can't just speak openly to DD about this, I nearly lost her before and I can't go through that again, plus he would have no hesitation in stopping me see DGD which would kill me. I just don't know what to do to make sure she is in this relationship with her eyes open, and seeing everything for what it is.
Mumsnet has not checked the qualifications of anyone posting here. If you need help urgently or expert advice, please see our domestic violence webguide and/or relationships webguide. Many Mumsnetters experiencing domestic abuse have found this thread helpful: Listen up, everybody
Relationships
How to tell DD her partner is unsuitable
SciFiScrewball · 29/08/2016 18:58
Sorry to hear this. All you can do is stay on the sidelines, encourage her to talk, keep pointing out she doesn't have to tolerate this and be ready to pick up the pieces.
Heartbreaking 
I think you do need to speak to DD about it. Gently though, tell her it's a difficult conversation and the last thing you want is to upset her or fall out. Tell her you are worried about his aggression with DGD and wonder if he is controlling like that with her.
Tell her you really do only have her best interests at heart and if she wants to stay with him you will continue to love and support her, and welcome him in to the house/family etc (as hard as this may be for you, you might have to)
Also tell her that you are not judging her or the relationship, but if there is ever anything she wants to talk to you about, you will always be honest with her but never judge.
You have a right to be concerned about your DD and your DGD and only have their best interests at heart. Just remember not to demean him or put him down because it will only make her dig her heels in and/or stop telling you things.
Good luck, it's a tough situation to be in.
If she doesn't want to listen, all you can do is be there to pick up the peices.
Having been the daughter in this situation it's difficult. Looking back I got very defensive and angry when my mum criticised the relationship or pointed out things that were wrong. I know my mum was devastated, and eventually moved further and further back. She was despite this always "there" for me though. (There's always hope for you, i'm now very happily divorced and very close to her).
I think in hindsight, even if somewhere inside you know things are wrong, you do feel very very trapped, so criticism is quite threatening and scary, because it feels like someone is trying to make you see the flaws but not offering a way out.
I think what might have helped more is tiny but consistent 'drips' of support in the way of pointing out where to go for help, but then pulling back. So mentioning books, women's aid, counselling, even where she could stay (your house?/ you help with rent) etc She still might get angry but you're not just criticising, you're offering her glimpses of a way out. I used to get angry if my mum said anything negative because to me it felt like she was highlighting my difficulties which I had no way out from. I'm sure she just felt she was trying to make me see sense.
Above all, don't give up on her, and let her know you'll always be there for her. Ignore him as much as possible, and be civil, so he can't try to get her onside against you.
I hope it works out for you. Keep building her self esteem too, and tell her what a lovely mum she is, because as you know, he's obviously trying to undermine her with the "I trust you" nonsense.
Thank you MakeitRain. That makes a lot of sense. She is however making the relationship more permanent by marrying him soon. She is so much under his spell it's frightening, but as you say, all I can do is just be there for her and offer support.
Thanks again all
To comment on this thread you need to create a Mumsnet account.