For people on the move, family reunification has become a major ‘channel’ to Europe and the ‘right to family’ is a widely recognized principle in international human rightsprotection and domestic legislations. Yet in practice exercising this ‘right’ is oftendifficult and migration buraucracies leave applicants unsure not only of the outcomeof their applications but of the criteria that are relied on in the decisions. In this articlewe analyze this dynamic via the case study of Finland and a close analysis of 253 ap-peals on family reunification applications at the Administrative Court of Helsinki be-tween 2003 and 2014. Our sample includes all decisions that mention ‘DNA,’ which hasbecome a routinely utilized biotechnological tool in family reunification applicationsinternationally. Our analysis focuses particularly on the 51 cases in which DNA testinghas confirmed the existence of biological family ties but the applications have, never-theless, been rejected. This article is contextualized in scholarship analyzing the recentspread of biotechnological tools and biometrics in immigration management. Simultaneously we discuss the quest for ‘information,’ ‘certainty’ and ‘truth’ that char-acterize family reunification applications. Relying on the recently flourished ethnog-raphy of documents, this article is ultimately about the indeterminacy and intrinsicsuperficiality of ‘the law. (Less)