Together the firms serve one in 12 families and hold more than £6bn of assets under management.
At the same time the new insurer is unveiling OneFamily Foundation, where the mutual’s members will decide how to invest £5m in five years in the communities they live in.
Simon Markey, chief executive of OneFamily, said: “This is a momentous first step on our journey in creating a modern mutual - a mutual that enables families to work together to meet the financial demands of modern life.
“It’s clear that personal finance has become family finance. Our research tells us that families are struggling to find relevant products that meet their changing financial needs and so are turning to one another for help.
“OneFamily will look to combine our commercial success with enduring mutual values to offer a compelling combination of relevant products, excellent service and customer benefits, that genuinely put our members first.”
The insurer's own research, in collaboration with YouGov, has found that only half of British adults (45%) think their high street bank has sold them the right product, while nearly three in five (38%) don’t trust their banks compared to 6% about mutuals.
OneFamily said the withdrawal of government spending and lack of support from banks means families are increasingly having to look across generations for financial help.
