Royal London has wholly acquired later life lender Responsible Group after initially holding a 40% stake in the business.
The mutual insurer said the deal, which is subject to regulatory approval, strengthens its position in the later life lending market for both advisers and their clients.
The later life mortgage broker and lender was founded in 2010 and is made up of Responsible Life and Responsible Lending.
Group chief executive (CEO) Barry O'Dwyer said: "This transaction strengthens our support for advisers and customers as they look for solutions in funding later life needs. We believe this market has a lot of potential as it offers customers additional choices at retirement, especially those who have property wealth but insufficient pension savings to support their desired standard of living.
"Later life lending is complex by nature and requires specialist advice. Royal London is keen to play a role in ensuring high-quality advice is an accessible option for those who would benefit from accessing the equity in their home."
Responsible Group CEO Carlton Hood added: "I am delighted that the Responsible companies are becoming part of the Royal London Group and will benefit from the stability of being part of the UK's largest life, pensions and investment mutual.
"We will work with colleagues at Royal London to bring the consideration of pension wealth and property wealth together for advisers and clients, and to ensure the advisers we support, and the customers they serve, are able to access the best range of later life lending solutions for their retirement needs."
