Parenting a child with a neurodevelopmental disorder (NDDs), such as autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), or intellectual disability (ID) can negatively impact family well-being indices such as family quality of life (FQOL), coparenting quality (CQ), and parenting stress (PS). The limited research examining birth order and number of children in NDD populations suggest that having a child with a NDD earlier in the birth order and having a higher number of children may place more strain on the family system. The current study aimed to explore how birth order and number of children are linked to FQOL, CQ, and PS in neurodevelopmentally diverse families as well as the influence of child group membership on these relationships. Mothers of typically-developing children (n = 56), along with mothers of children with ASD (n = 69), ADHD (n = 127), and/or low intellectual functioning (n = 30) between the ages of 6-12 years old completed an online survey. One-way MANCOVA analyses revealed no significant differences in the ASD, ADHD, or low intellectual functioning groups, however, in the TD group, mothers of children earlier in the birth order reported significantly higher PS. Two-way MANCOVAs showed non-significant interactions between birth order and child clinical group membership in the ASD and ADHD groups, but significant interactions in the low intellectual functioning and TD groups. Regarding the number of children, no significant differences in FQOL, CQ, or PS were found for families of children with ASD, ADHD, or TD children, though mothers of children with low intellectual functioning reported significantly lower CQ when they had fewer children. Finally, a one-way MANCOVA found no significant differences in FQOL, CQ, or PS between families with one child with a NDD versus multiple children with a NDD. Post-hoc analyses revealed significant main effects of child symptomology, indicating that families of children with NDDs are at an increased risk for lower family well-being. The results of this study highlight the unique needs of families of children with NDDs and families of TD children. Additionally, these findings emphasize the importance of providing additional supports to families of children with NDDs.