Police are investigating the killings after a female and her chick were found dead in their nest at the end of May.
The male eagle appears to have picked up a piece of poisoned bait and brought it back to the nest where it was eaten by the other birds. Ornithologists assume the male is also dead, although no remains have been found around the nest, which is in the Kingussie area of Strathspey.
A post-mortem examination on the female and her chick revealed lethal quantities of Carbofuran, a highly toxic insecticide. It has been illegal since 1953 to use the substance to kill birds of prey, but some landowners still put out bait for eagles to protect their stocks of grouse, according to the Royal Society for the Protection of Birds in Scotland.
An RSPBS spokeswoman said: "Typically a rabbit would be laced with insecticide and laid out on open moorland. There have been several cases of dogs belonging to hill walkers being affected.
"If those responsible were caught they would face a fine of up to pounds 5,000 but it is very difficult to find the people guilty of these crimes, because they are usually committed in out- of-the-way places where there are few witnesses."
She said it was unlikely that the birds in this case had died because of secondary poisoning - capturing and then eating an animal that had been poisoned.
However, there have been such incidents during the summer. In the north of Scotland a family of red kites died after eating a rat that had itself consumed poison.
The RSPBS spokeswoman said there had been only one similar incident of two golden eagles from the same nest found poisoned, and that had been 10 years ago.
Dave Dick, a senior investigation officer for the society in Scotland, said: "There are 430 pairs of golden eagles all over Scotland. Fortunately this is a rare event. A lot of sites are monitored by volunteers."
Now that the golden eagles are no longer resident at Strathspey, other birds will move in to take their place. Because they will lack experience of the territory, other wildlife will be less vulnerable until the newcomers become familiar with their surroundings.
Officers at Northern Constabulary investigating the case said it is now unlikely that anyone will be charged over the incident. They condemned the poisoning as "utterly irresponsible" and warned that using poisons could also put the public at risk.