How to help daughter cope in a second marriage

Hard as it might be they don't. Dont get involved unless asked, particularly if the problem is concerning the ex wife. Somewhere along the line you will be accused of interfering so best to avoid at all costs.

My elder son is in his second marriage with 3 children from his first, which spend roughly an equal amount of time with both parents. There have certainly been issues between him and his first wife, but his present wife has always treated these as problems for them alone to work out- although of course fully supporting her husband. This certainly would be my advice to you - generally support her and her husband but DO NOT become personally involved with the relationship between him and his first wife or be tempted to make disparaging remarks.

What if first wife has a stronger relationship with my daughters in-laws which husband finds upsetting too?

Still a problem for the husband, his ex and his parents to sort out.

My daughter did not split up first marriage - ex wife's decision a year or two before my daughter was around.

Have I understood this right? The problem is that your son-in-law was married to someone else before he married your daughter but your daughters-in-law (married to sons of yours) have a good relationship with the person your son-in-law was married to first. This upsets him and is a problem for your daughter who is now married to him.

Is that right?

In any case, I agree with those who have said don't get involved. They are adults. Let them sort themselves out.

Yup - stand back, keep out, let them sort it out themselves. If she broaches the subject then you can reasonably say that it is not right for you to get involved/take sides etc and that you have every confidence that she will deal with the situation well.

I think its a problem of the ex wife still being friends with the husbands parents. If that's right its still his problem to sort out.

The best and only way to help is to listen, nod sympathetically and let her know you love her and will always be there for her. Never give advise, or actually do anything.
I had so many problems with first half of my second marriage due to my OH's 'baggage' ....it was all so complicated...the situation itself i.e. the 'facts' then there was his attitude to it, my attitude, the affects upon the children...etc etc. All my Mum ever did was listen and smile......it was the best thing to do, anything else just opens up a hundred and one more 'cans of worms' believe me....if its complicated for those within the relationships to gets to grips with it all, its impossible for others and its actually dangerous for others to get involved....it can and will blow up in everyone's face.

I'm still friends with my ex-husband's parents. I'm still friends with him! It doesn't need to be a problem. Just be civil to everyone and hope that they behave like adults.

Thank you everyone. I know I need to stand back. There is an enormous amount of baggage with all persons involved which I feel I cannot reveal here - some counselling might help but it needs to be professional - not from me. My daughter just needs to sound off now & then. My ex left me when she & her brother were small so I tend to be overprotective, though NOT a dominating mother. I am very fond of my son-in-law. Just wish he could sometimes stand up to his mother when she is - unintentionally- hurtful re her relationship with his ex wife. Oh dear what complicated life's we all live these days!!
Thank goodness for wonderful girlfriends.

It is perfectly normal to be friends with the ex wife.
My friend is divorced but it hasn't changed her relationship with her ILs, they have a long history because she met them aged 16 yrs. she has just been on holiday with her ex SIL. You don't just wipe it all out because there is a new wife. She makes her own relationships. There will be baggage. You are quite right in that if counselling is needed it should not be from you. It is hard to just stand by and not interfere - but it is the best advice.