It is fairly common for multiple members of a family to have ADHD. A clinical sample of parents of children with ADHD was found to have ADHD themselves (41.3% of mothers, 51.0% of fathers); the inattentive subtype is the most common, then the mixed subtype and hyperactive subtypes respectively. Additionally, younger siblings of those with ADHD are 13x more likely to also have ADHD. These younger siblings also have an increased risk of developing ASD.