This paper aims to present the first results of an investigation based on the transmission of Spanish as a heritage language (HL) in young (30-42 years old) heterosexual binational families in German-speaking Switzerland. The sociolinguistic study with an entographic perspective combines the recording of daily family interaction events of 10 families over a period of five/six months (depending on the families) without the presence of the researcher with semi-directed interviews conducted with the parents separately, as well as focus groups with the male parents. Of these, five are German-speaking Swiss and five are Latin American (from Argentina, Mexico, Peru and Uruguay). The qualitative analysis of the data, which triangulates interactional analysis, discourse analysis and content analysis, shows the importance of male parental agency in the transmission of Spanish, regardless of whether it is the father or the mother who is a Spanish speaker. In the 10 cases studied, male fathers assume an active role in the transmission of Spanish as HL. This agentive role, as well as their metadiscourse, evidence the existence of language policies based on positive linguistic ideologies towards the maintenance of Spanish due to the different affective, relational and functional values they ascribe to Spanish. Furthermore, with respect to another previous study carried out by the researcher, based solely on interviews, and where Latin-American Spanish speaking mothers  over 50 participated, a change of ideology and agency is observed with respect to this new generation of male parents, demonstrating that fathers of the new generations are currently actively involved in family language policy.