Background: Sexual development is a complex process, the study of which should consider not only first sexual intercourse but also multiple behavioural trajectories in a comprehensive perspective. Moreover, first romantic relationships and sexual experimentation during adolescence form the building blocks for subsequent more mature relationships and sexual behaviours later in life.

Objective: This study focuses on young Italians’ first romantic and sexual experiences, with a twofold aim. We seek to both describe the trajectories characterising the first stages of youths’ affective and sexual development and to study the differences among them by gender and birth cohort.

Methods: Applying sequence analysis and subsequent cluster analysis to a sample taken from two surveys conducted in 2000–2001 and 2017 on Italian university students, we identify young people’s affective and sexual development trajectories. This is followed by a multinomial logistic regression analysis to discern the effect of gender and birth cohort on the probability of belonging to a given pathway.

Results: We identify six distinct sexual ideal types among young men and women, with gender differences that characterise the trajectories of affective and sexual development of most university students. That said, our results also suggest that differences between the two genders have narrowed over time.

Contribution: The findings confirm the importance of not only considering first sexual intercourse and the ‘typical’ trajectory of affective and sexual development but also accounting for diverse trajectories so as to accurately capture the complexity of youths’ early romantic and sexual lives.