Analysis of Office for National Statistics (ONS) data by wealth manager St James’s Place suggests there will be 1.2 million ‘multi retiree’ families by 2039, up from 624,000 today and 328,000 in 1999.

This changing family structure means people’s retirement income will need to stretch further.

A survey of 4,000 adults found a quarter (24 per cent) of people already expect to financially support someone other than their current partner in retirement, such as children or grandchildren. This compares with 7 per cent who do at the moment.

Future retirees anticipate having to help other generations with everyday living costs, school or university fees, and childcare.

Over a fifth of people surveyed said they felt pressurised or worried about the prospect of providing financial help to other generations.

They also expect to pass on much smaller inheritances to their loved ones.

Current retirees expect to pass on around £124,600, whereas future retirees expect this number to be nearer the £74,000 mark.

Claire Trott, head of pensions strategy at St James’s Place, said: “Passing wealth on to our loved ones is one of the final acts of kindness we are able to make, so it is concerning that the amount many believe they will be able to pass on is eroding.

“However, that needn’t be the case.  Putting in place the right plans at an early stage will allow greater opportunity to build wealth over time and leave behind as much as possible when you’re gone, without making unnecessary sacrifices along the way.”