By 1964, John, Paul, George, and Ringo were all in steady relationships- John was married to Cynthia while Paul, George, and Ringo were all dating Jane, Pattie, and Maureen. They would frequently visit each other's homes, even staying overnight or two, celebrating Christmas all together. It was having an extended second family; there was even a few considerations about buying an Island near Greece for all of them to live on as well as an idea of one big mansion like a commune. The relationships and the get togethers would last until 1968 when Paul and Jane break up, John and Cynthia divorced.
Although after both breakups, including the Beatles' break up in 1970, the 'second' family tradition continue on with other wives and girlfriends who joined in the circle today.