Family trees initially seem innocuous and mundane. However, as an ongoing “project of mobility” which (re)shapes “family,” family treeing can (im)mobilise relations with past, present and future kin in ways that shape and are shaped by past, present and future narratives. In this theoretical and speculative paper, I explore this thesis by taking a special interest in childless family members and in understanding how practices of family treeing enable or prevent their stories, and even knowledge of their existence, from travelling through time. The article contributes to debates on family and intimate mobilities by showing that in addition to the complex assemblage of mobilities that maintain social connections in the present, family mobilities involve i) mobilities of knowledge, in addition to physical mobilities and ii) connectivities that stretch into longer timeframes than those discussed in family and intimate mobilities to date. The article also contributes to debates on mobility and memory by exploring the mobilities of different kinds of intergenerational knowledge, and their possible significance in (re)producing ideas of “family.” The significance of these ideas is explored through a discussion of family members in the present who are childless-not-by-choice, and their lived experiences of bereavement, taboo, meaning and legacy.