Nearly a third of grandparents only see their grandchildren once a month - or even less frequently - according to a survey released today.
The study into loneliness in older people found that as well as 32% of over-65s only having monthly visits to see their grandchildren, the same percentage see their own children fortnightly or less.
A fifth (21%) of the 1,242 people surveyed by Age UK only see close friends every two weeks and one in five said they found it harder to speak about loneliness than other issues.
A separate study for charity YouthNet showed that loneliness crosses generations, with 19% of the 1,101 surveyed saying it is the thing they most fear about the future.
Michelle Mitchell, of Age UK, said: "We already know that loneliness affects over a third (34%) of people aged 65-plus in Great Britain.
"Modern day life means that more people live further away from loved ones, so seeing older relatives regularly can be increasingly challenging.
"By bringing older and younger people together in their local communities through a new digital service we hope to go some way in helping to reduce isolation and loneliness across the generations."
The two official Virgin London Marathon charities are joining forces to tackle isolation. They are calling for runners to raise money for a new service that will see young people volunteer to help isolated people learn how to use the internet, so they can stay in touch with people and find out about new hobbies.
Emma Thomas, CEO of YouthNet, said: "There is so much that young people can contribute to society and helping older people to benefit from online and connect with their families so they feel less isolated is a great example of this."
Age UK and YouthNet have 350 guaranteed London Marathon places for their team, Team Run for It.