“…Of all family relationships, sibling relationships have the longest duration (Cicirelli, 1995; Matthews, 2002; van Gaalen, Dykstra, & Flap, 2008; Voorpostel, Dykstra, & Flap, 2007; Voorpostel, van der Lippe, & Flap, 2012). The development of strong adult sibling relationships forms an important source of support for adults over the life course (e.g., Cicirelli, 1995; Eriksen & Gerstel, 2002; Kalmijn & Leopold, 2019; Milevsky, 2005; Spitze & Trent, 2006; Voorpostel & Blieszner, 2008; Voorpostel et al, 2007; White & Riedmann, 1992).…”