LONDON, Aug. 7 (Xinhua) -- Cohabiting couple families have become the fastest-growing family type in Britain over the decade 2008-2018, figures from the British Office for National Statistics (ONS) revealed Wednesday.

The growth of cohabiting couple families continues to outpace that of married couples and lone-parent families. It has become the second-largest family type in Britain, with an increase of 25.8 percent over the past decade, accounting for 17.9 percent of the total families, said the ONS.

The figures show that married and civil partner couple families remain the most common family type in Britain, representing 67.1 percent of all families.

The number of people living alone in Britain in 2018 has surpassed 8 million, up from 7.7 million in the previous year, driven by increases in women aged 45 to 64 years and men aged 65 to 74 years.

The number of same-sex couple families has grown by more than 50 percent since 2015, with more than four times as many in 2018 compared with 2015, said the ONS.

A quarter of all young adults (3.4 million) aged 20 to 34 years were living with their parents in Britain in 2018, said the ONS.

"The ways that people live have been changing," said Sophie Sanders, head of demographic analysis at the ONS, adding that people increasingly choose to live together before, or without, getting married.

"There are also more people living alone than ever before, an increasing number of same-sex couple families and more young adults living with their parents," she added.