But there are problems. It is not easy to share experiences down the telephone or across a continent. Many families live apart and grandparents may only see their grandchildren once or twice a year. Others may feel they see too much of them if they provide childcare for working parents.
At its best, the relationship is rewarding for both parties. 'Children tell their grandparents many things they don't tell their parents because the grandparent has more time to listen,' says Robert Snowdon, Professor of Family Studies at the University of Exeter. 'They are also more willing to put up with the exhaustion of amusing a small child because it is temporary.'
But if the parents' relationship crumbles, many grandparents are left struggling to stay in contact. Norine Tingle runs the Grandparents' Federation, set up to campaign for grandparents to be allowed access to grandchildren in local authority care, and she has seen the despair of grandparents denied contact. 'I compare it with the terrible sadness that women feel who can't have children. They are bereft.'
The Children Act of 1991 allows grandparents to ask the court to be heard on the question of access, not just in care cases but also after divorce, and the Federation has helped thousands to press their case. 'They might not get the sort of contact they want,' says Norine Tingle, 'but I think most grandparents will settle for anything rather than nothing.'
When a break-up is followed by remarriage, grandparents may find their grandchildren becoming the step-grandchildren of another couple. There can be four sets of grandparents, and it is hard for grandparents suddenly to have to share their grandchildren. They may also acquire step-grandchildren of their own and have little idea of what is expected of them. One woman, whose daughter married a man with four children and then had a baby of her own, admitted: 'I'm longing to spoil my daughter's baby but she wants me to treat all the children the same. I do care about the others, but it's difficult to make a pension stretch to cover five Christmas presents.'
The National Stepfamily Association receives many calls from anguished grandparents. One problem with step-grandchildren is that, traditionally, grandparents pass on the family history - this is what your mummy was like when she was your age, this is what my father was like - which is meaningless when talking to a step-grandchild. But Stepfamily Association counsellors remind callers that a child does not understand the difference between a real and a step-grandparent.
Now a new question is looming: who is the grandparent? Professor Snowden has been looking at children born by donor insemination (where the mother's egg is fertilised by sperm from an anonymous donor) and observes: 'I see families where the wife's side all know about it, and the husband's side have been kept in the dark about the baby's origins. They seem to suspect the husband's family would not accept the grandchild if they knew there was no genetic relationship.
'Marriage has always been the vehicle by which two distinct groups of people become related, especially when children are born. In donor insemination that is dislocated and we haven't seen the long-term effects yet.'
'The Children Act: What's In It for Grandparents' is available for pounds 2 (inc p & p) from The Grandparents' Federation, Moot House, The Stow, Harlow, Essex CM20 3AG. The National Stepfamily Association offers counselling on 071- 372 0846; or general information on 071-372 0844.Reuse content