we don't know what happened in 2014 other than Durbe and Robert raised three eaglets successfully. that happened in the old nest which was destroyed in the end of the season. they built this nest in the next winter.
in spring 2015 Durbe laid two eggs but a crow ate one of them. in that season there were so much fish that i have never seen so many! twice as much rotted on the nest than the eagles (Durbe and Angelina) could eat. Robert was a great fisher!
in 2016 and 2017 were the years when several eagles competed for the possession of this territory.
WTEs are not 'regular' eagles in what comes to sibling rivalry. it is not very pronounced in them. last year's eaglets were exceptionally violent towards each other. i have never seen anything like that before. usually the pecking stops by the age of 10 days - two weeks. sibling rivalry is much more pronounced in 'real' Aquila eagles to the extreme of cainism. in those species usually only one eaglet survives.
the amount of food regulates the egg numbers in owl species. if the female does not get well fed she will be able to lay fewer eggs than in a good vole year. if there is very little food she may not produce any eggs at all. if the food situation continues to be bad or becomes bad after chicks have hatched some of them will starve to death before fledging. even the parents may starve to death in the spring/summer if food supplies vanish.