Developmental Delays and Disabilities (DDDs) refer to conditions where children are slower or unable to reach developmental milestones compared to typically developing children. This can cause significant stress for parents, leading to social isolation and loneliness. Online videos, particularly those on YouTube, aim to support these parents and caregivers by offering guidance and assistance. Studies show that parents of children with DDDs create videos on YouTube to enhance authenticity and build connections. However, there is limited knowledge about how other parents with children with DDDs perceive and are impacted by these videos. Our study used a mixed-method approach to annotate and analyze more than fifteen hundred YouTube videos on children's DDDs. We found that these videos provide crucial informational content and offer mental and emotional support through shared personal experiences. Comments analysis revealed a strong sense of community among YouTubers and viewers. Interviews with parents of children with DDDs showed that they find these videos relatable and essential for managing their children's diagnosis and treatments. We concluded by discussing platform-centric design implications for supporting parents and other caregivers of children with DDDs.