The extension of life expectancy results in a substantial increase in the number of very elderly people and four-generation families becoming commonplace. Yet, we know little about great-grandparents' roles and the parts they play in the family. The authors have taken a specific interest in great-grandfathers and in their great-grandchildren's viewpoint. Interviews with three independent great-grandfathers living at home near their descendents as well as with eight of their great-grandchildren aim to shed some light on the eldest's situation in the family. The drawings and observations of young children (aged 5 to 14), along with the interview of their great-grandfathers, enable the authors to suggest that, although the great-grandfathers' position in the genealogy is perfectly well grasped, their role in the family seem more difficult to define; doubtless, due to its tenuousness. Separated by two intervening generations, young children and the parents of parents of one of their own parents seem not to have many verbal interactions nor shared activities, even if they meet every day. On the other hand, because they are perceived as being the "real" old people, great-grandfathers likely play a part in the way young great-grandchildren learn about old age. Children prove their ability to pick out the signs of old age in their great-grandparent: changes in the physical appearance, difficulties in moving and sensory weaknesses; and this keen perception of the troubles linked with ageing introduces them to an understanding of human finality.