H1The primary goal of this intervention study is to learn if very early parent-mediated intervention in children at risk for neurodevelopmental disorders in the first year of life can be implemented in routine care, positively impacting early sensory-motor and socio-communicative developmental trajectories and reducing the developmental gap in children with signs of concern. H2: It is here postulated that early intervention with active parental involvement can reduce parental stress, as well as improve parental understanding and responsiveness to the child's communication cues. H3: An important part of our work will be analysing data about early social and joint attention behaviours in recruited children and comparing them at different time points. The hypothesis is to find early differences between groups at baseline and to detect a change before and after the intervention. For this reason, in our study design, we decided to use technologies to collect data on quantitative measures during play-structured and laboratory sessions to understand changes in developmental trajectories. H4: Given the potential role of genetic and immunological mechanisms in ASD, one of the study's secondary aims is to investigate the impact of an early intervention programme on epigenetic changes and inflammatory and immune response. After enrolment and baseline assessments (T0), children will be allocated to the three groups: * Group 1 - Clinical Monitoring Group (CM): Siblings of TD children subjects with no signs of concern * Group 2 - Active Monitoring Group (AM): Siblings of ASD children with no signs of concern * Group 3 - Early Intervention Group (EI): Siblings classified as with signs of concern at baseline evaluation. All children will be re-evaluated after 6 months (T1) and after 12 months (T2).