Social relations between demographically dissimilar people are less likely to last. But up till now, why relations with dissimilar friends, confidants, or even sport partners are less stable has remained unclear. We argue that the faster dissolution of ties to dissimilar others may stem from their weaker embeddedness in our social networks. We may feel less emotionally close to those who differ from us in key social dimensions such as gender, age, and education, and these alters may fulfill fewer roles (e.g., friend and study partner, or ‘multiplexity’). Moreover, their dissimilarity may hinder their ability to form relations with others in our social network. In this contribution, we investigate the impact of ego‐alter dissimilarity on the stability of friendships, confidants, and study and sport relations, while acknowledging multiplexity—recognizing that the same alter may serve different roles. We find that ego‐alter age dissimilarity is associated with tie dissolution; relations are less stable and consistently so across emotional and instrumental network layers. Gender and education dissimilarity do not impact relationship stability among our sample of Dutch students. The better alters are embedded in ego's network, the more stable are their ties. Relational embeddedness (i.e., emotional closeness and role overlap) predominantly affects the stability of confidants and friendship relations; structural embeddedness (i.e., alters having ties to ego's other alters) predominantly affects the stability of study relations. This also explains why relations with differently aged alters are less stable.