But now a study has put a price tag on the unpaid babysitters that many parents couldn't manage without.
And that value is £4,300 a year – money that would have otherwise have to be spent on childcare.
Furthermore, by the time the average youngster reaches school age, they will have been babysat by their grandparents for more than 5,610 hours, meaning their parents will have saved a huge £21,654.60.
The study of 1,298 parents also revealed as many as one in four wouldn't be able to hold down their current job without the help of their elder relatives. Around half said it wouldn't be worth them going to work if the children's grandparents weren't around to help out.
Stacey Stothard, of Skipton Building Society, said: "As this study clearly indicates, modern day grandparents are an absolute god-send for working mums and dads.
"Despite reaching an age where they should be winding down and enjoying their retirement years, grandparents end up almost 'working' for their own children, making it possible for them to earn a living, safe in the knowledge that the little ones are well cared for.
"And as we can see, a grandparent's help is invaluable. Not only do they provide a safe and caring environment for the grandchildren to grow up in, but they save thousands of pounds in childcare fees every single year.
"They also provide that flexibility which parents would be hard-pushed to find with any nursery or child-carer."
The study revealed during term time, and for 39 weeks of the year, grandparents will help out on three days of the week for at least 5.5 hours a time.
This means they are acting child-carers for 16.5 hour per week or 643.5 hours over the course of 39 weeks. For the remaining 13 weeks of the year - the school holidays - the grandchildren will be looked after by their doting grandparents for a further 32 days, for an average of seven hours a time.
The poll shows that six in 10 parents prefer asking the grandparents to help out with childcare rather than paying a nursery or child-minder. Almost half of these claim that as well as the cost benefits, they simply don't trust anyone else to look after their child.
But four in 10 mums and dads do feel guilty about how much they rely on their own parents for help, and a third worry that they are getting too old to deal with overly energetic grandchildren.
And while six in 10 parents don't want to think about what might happen when their own parents get to the point where they can't look after the children anymore, a further 33 per cent are resigned to the fact they will eventually have to give up work to look after their own children.