Adopted grandchildren

My son adopted a little boy. Initially he was prepared to go along with his child seeing his biological sister, and they did see her a couple of times, but after she posted a photo of the little boy on Facebook, they declined contact, but said they could write to one another. However our grandson showed no interest in doing that, and so the relationship (which was never a big thing) died completely. Our grandson will of course have every right to search for his birth family when he’s old enough, should he wish to.

I realise it must be heartbreaking for you, but your biological grandchildren are now part of another family with grandparents, cousins etc and since you mention a disagreement with the adoptive parents, I’m not really surprised that they’ve shut down the relationship. It’s hard for you, but I think you have to accept the situation.

Making a mountain out of a mole hill is very subjective - the issue could be a very big deal for the parents of the children, but not for you

If you are in the UK, then this isn't something you need to sort out yourself.
The agency that arranged the adoption or the responsible local authority will have written in contact with you as part of the adoption agreement. Note, that if it isn't part of the formal agreement, then I am surprised that you have any contact at all.
So you can contact them and ask about contact arrangements. This can be done at a neutral venue, and arrangements made, such as no camera / mobile phone at the venue etc. It is best done formally through the agency, then personal disagreements don't come into it.
I'm afraid that I can offer no suggestions if you are under a different legal system.

Nannarose

If you are in the UK, then this isn't something you need to sort out yourself.
The agency that arranged the adoption or the responsible local authority will have written in contact with you as part of the adoption agreement. Note, that if it isn't part of the formal agreement, then I am surprised that you have any contact at all.
So you can contact them and ask about contact arrangements. This can be done at a neutral venue, and arrangements made, such as no camera / mobile phone at the venue etc. It is best done formally through the agency, then personal disagreements don't come into it.
I'm afraid that I can offer no suggestions if you are under a different legal system.

I think open adoptions are quite common in the US ?

Surely this is a matter for the professionals who undertook the adoption, tbel?
What was the agreement at the time of the adoption?

'Open' adoptions are fairly well known in the UK, but depend on individual circumstances, and there are often reasons for not allowing them. My experience is that in the UK, the conditions for contact with the family of origin are clearly set out (which makes me wonder if OP is not in the UK)
When I was a Health Visitor, I dealt with a few US adoptions and found that adoption laws in the US vary from State to State, so can be very complex.

We just got done spending the night at their house babysitting. My daughter and son-in-law were in from Alaska and are the same age so they went up North for the weekend.
We've had an awesome relationship with the couple for the past 2 years. Hard to think all that has ended because of a disagreement one night. All happening while my daughter and her husband from Alaska are cooking dinner for all of us.
Incredibly sad.

Is this daughter a different daughter, or is she the mother of the children?

Message withdrawn at poster's request.