The characters are played by the same actors ´cause (specially in this film) Medem reinforces the cyclical sense of the life, the mistakes and weaknesses of the parents are suffered afterwards by the children. I can´t remember it very well but for example, the first chapter it´s called el aizkolari cobarde (sorry I don´t know how it´s called in english) ´cause the first character pretends to be dead to scape from the horror of the war and at the end of the film, we can see his grandson doing the same when emma suarez is laying in the forest , he pretends to be american (not a spanish speaker) to avoid his execution and save his life, leaving her alone. At the end, he is back to take care of her, she awakes in the same moment he arrives to her side (she thinks he has been all this time with her) , and he says something like I will always be with you... or something like that, and that´s not true. it´s the same with the relationships between the families along generations.
it ´s an example of the life in the little villages where the discussions or relations between families keep on being the same although the years go by.