Emma Noble had a dream of happy families. When her baby son was born, she moved house to be close to her in-laws, John and Norma Major. Emma imagined they would hang out together in their free time as one big extended family. What she failed to do was to check with the Majors first.

I'm guessing that she also thought child care would be divvied up between the Majors and her own parents (who also moved close by), leaving her and her husband free to work. An increasing number of young working parents make this presumption.

For Noble, the dream evaporated when her famous in-laws failed to conform to expectations. Then her boy was diagnosed with autism and shortly afterwards her marriage broke up. Six years on, her parents do much of the child care. Now she is accusing the Majors of neglecting their grandson. It's an accusation they refute.

Given the chasm between what is expected of grandparents in today's world and what grandparents expect to give, both Noble and the Majors are very possibly telling the truth as they see it. So what constitutes a good grandmother and grandfather? What are grandparents' rights and what are their duties? Where does extended family end and slave labour begin?

I always think I have an insight into grandparenting because I was by far the youngest in my family and was an aunt before I was 10. I spent my teens watching my parents prepare for, enjoy, endure and then recoup from visits from their expanding tribe of grandchildren. By the time I had added my own, they had 15. Were they "doting" grandparents? Sometimes they doted; sometimes they were neutral; and sometimes they tolerated. The variation is perfectly natural.

My parents were consistently kind. But, in truth, while they loved their children equally, they had a cooler eye on the next generation. It wasn't unusual to hear my mother say: "If I had my hands on that rascal for a week" The parents of the rascal were oblivious to the intolerance. Night after night they would allow their treasures to scream themselves to sleep as the baby manual dictated - while granny itched to lift the infant - and/or allow the toddlers to rampage until they dropped with exhaustion instead of establishing an early evening bed time.

The longer and louder the visit lasted, the higher the zing of tension in the air. Miraculously, I don't recall a fall-out, just the glorious relief when it was all over for another few months. I learned two things: first, that it's natural for grandparents to like some of their grandchildren more than others; second, that the better behaved your children are, the more popular they will be.

My parents did, for a time, help one sister with after-school care. For the rest, they offered holiday hospitality, birthday and Christmas cards, modest presents and a cash tip when they saw a child. Isn't it enough? I think so but it wouldn't rate as commitment to today's young parents. They seem as greedy as gannets when it comes to granny and grandpa - especially when it comes to commandeering their time. There are an estimated 14 million grandparents in the UK and statistics suggest that they do a staggering 60% of the childcare. Some grandparents even shunt between cities to look after their sons' and daughters' children - usually for free.

These are people who have raised their own children and often looked after an ageing parent. If they had plans to spend their twilight years painting, golfing, learning to salsa or seeing the world, they've had to postpone them. They are under pressure because of this new expectation that they will help out their children. The young parents are probably both working. They may have a big mortgage and will frequently factor in granny and grandpa as free child-care. Like Emma Noble, many don't discuss it before hand. Unlike the Majors, most grandparents don't dare resist.

They feel guilty and selfish for wanting to put their own lives first. It is complicated because they love their children and want to do what is best for them. They love the sense of family and many do adore the grandchildren. But looking after small people is very hard work. To do it for one son's or daughter's baby means doing it for all. With no proper payment of any sort, it can leave people feeling trapped, exhausted and aggrieved.

Complaints must, however, be left unspoken, as must opinions. At the merest breath of criticism sparks would fly. Unlike normal employees, grandparent child- carers must never express an opinion, demand rights or request an income. Some are not even offered expenses. When they take their grandchildren to the cinema, zoo or pizza parlour, it comes out of their own pocket. Yet surely if a salary isn't appropriate, there should be some recompense - such as a luxury hotel break, a new outfit or a winter week in the sun. Yet I know grandparents who child-sit all year and then watch the parents treat themselves.

It's why grannynet.co.uk advocates a grandparents' charter of rights. Its founders say it is vital to establish a set of ground rules before the commitment starts. It's no good rushing in with offers when the first grandchild arrives. It could be the first of many and with age and decrepitude childcare gets harder. Ground rules also offer an advantage for parents. They can contain an overbearing granny who doesn't know when to step back. With so many families fractured, some grandparents are acting as lifelines. Every year, 200,000 of them take in their grandchildren to keep them out of care. It happens when parents die or are ill; also when they are addicted to drink or drugs. Some of the children are the product of short-term relationships, some are step-grandchildren. Grandparents are estimated to save the state £4bn a year.

Perhaps the saddest group of all are those who are denied access to their grandchildren. I know two grandmothers in this situation through no fault of theirs. It causes real on-going heartache to the older generation and robs the grandchildren of a hugely important relationship.

There is a bond between the young and the old that cannot exist between a parent and child. Freed from the necessity constantly to correct behaviour, grandparents can indulge in irreverent play. They have time to listen and time to hang out. Grandfathers do old-fashioned things such as identify butterflies or tie fishing flies. Grandmothers bake and own clothes that are good for dressing up. Both are role models with standards of behaviour often far higher than the generation between.

Research carried out at the Centre for Research into Parenting at Oxford University noted the very high percentage of informal childcare offered by grandparents. It also noted that adolescents who spent time with grandparents were measurably happier than those who did not.

Happiness is a payback that grandparents will treasure. But parents need to waken up to the reality that their child's happiness doesn't cancel their debt of gratitude.

It adds to it.