... Although no studies have examined the relationship between PDT and estrangement, parental preference of one sibling over another is linked to poorer sibling relationships from early childhood through adolescence (Richmond, Stocker, & Rienks, 2005;Shanahan, McHale, Crouter, & Osgood, 2008). Likewise, in adulthood, sibling relationship quality diminishes with increased parental favouritism (Gilligan, Suitor, Kim, & Pillemer, 2013;Jensen, Whiteman, Fingerman, & Birditt, 2013) and is PDT is associated with reduced psychological well-being (Jensen, Nielson, & Yorgason, 2019;Pillimer, Suitor, & Henderson, 2010;Suitor et al., 2017). It is not just current perceptions of differential treatment that affects psychological wellbeing and the quality of the sibling relationship in adulthood, but brothers and sisters' recollections of differential treatment in childhood (Peng, Suitor, & Gilligan, 2018;Suitor et al., 2009). ...