A record number of people are getting help from family members to enable them to buy a house.
Financial support from the "bank of family" is expected to help with 318,400 property purchases this year, according to Legal & General (L&G).
Some 47% of all homes bought by those under the age of 55 will have been done so with the help of parents, grandparents or other relations.
But L&G said those without such support risk being "locked out" of the market.
The financial services group has been tracking support from families for homebuying for the past seven years, and it said that in 2023 more people than ever are relying on relatives' help for a deposit.
L&G used to refer to the support as the "bank of mum and dad", but has changed this to the "bank of family" as it said the term more accurately reflects the contributions from other relatives, such as grandparents, and the diversity of modern families.
Total lending
It found that the average amount given by families to loved ones is expected to hit £25,600 this year, with total lending set to reach £8.1billion.
In 2016, when it first carried out the research, total lending was £5.3billion.
Separate research from Hamptons estate agent and Skipton Building Society suggests that brothers and sisters are also becoming an increasingly important source of funding.
It found that, of the family members contributing to first-time buyer deposits, siblings made up a record 11%, more than double the 5% share seen five years ago. On average they donated £10,250.
L&G said that house prices have been growing at a much faster pace than wages, and with the cost-of-living crisis and rising interest rates, it is becoming increasingly hard to buy a property without family support.
"Whilst the majority are mums and dads helping out, also grandparents, aunts and uncles and even friends of the family are helping out as well...in ever-increasing amounts of generosity," Bernie Hickman, chief executive of Legal & General Retail, told the BBC.
Property ladder
However, he added that, while nearly half of those buying a house under the age of 55 are doing it with family help, "the flip side of that means that if you're not, if your family isn't in a position to support you, it becomes that much more difficult to get on the property ladder".
Mr Hickman also said that families were also giving much more non-financial support, such as allowing adult children to live at home rent-free while they save for a deposit.
One-in-five of those surveyed by L&G said that without family support, they would have to delay their home purchase by more than five years, while one-in-10 said they would not be able to buy a home at all.
"Family wealth is increasingly becoming a prerequisite for homeownership, effectively locking some groups out of the housing market for years while they save for deposits, or even altogether," said Mr Hickman.