Despite looking after their five-year-old grandson and four-year-old granddaughter for three years, social workers decided they were "too old" and unsuitable to continue.
And, tragically, the children now think that their grandparents are dead.
"Social workers made up their minds that we were too old," says the grandad, who is 59. His wife is just 46 and both look much younger.
"It just breaks my heart and eats away at me every day. My own grandchildren have been wrenched away and now they think that me and their granny are dead."
The children went to live with their grandparents because their mother, a heroin addict, couldn't look after them. The boy's father is dead and the girl's father has not had any contact with her.
But social workers later insisted the children would be better off with the two gay men. "My wife and I were happy bringing the children up ourselves," says the grandfather.
"We are their family. Now we've been told we'll never see them again. How can that possibly be right? They are our flesh and blood."
The children have now been given new identities and totally removed from their former life, family and friends.
The only contact their grandparents have had with the children in the last eight months is a two-paragraph letter from their new parents giving a few scraps of news about the pair.
The case provoked a storm of criticism in February when the adoption was first revealed.
The grandparents and children cannot be identified for legal reasons so we are calling the boy Adam and his sister Katie. We are calling their grandparents Brian and Margaret.