“Long and thin in form as older generations live longer and affinal ties are weakened by divorce in the middle and younger generations” (Brannen & Nilsen).
“Vertical relationships within families have become more important especially in recent years in Britain, due both to increased possibilities and to greater necessity” (Brannen, Moss, & Mooney 2004).

As defined by Brannen & Nilsen citing Bengston in Adulthood: Changing Concepts and Definitions entry.  Brannen, J., Moss, P., & Mooney, A. (2004). Working and caring in the twentieth century: Change and continuity in our generation families. Basingstoke: Palgrave.