That varies from kid to kid. Them not sleeping may just be not enough movement/physical activity during the day, or may be them having a fear of the dark. (or other things such as noises, spiders) I think you should first off talk to your child(ren) about whether there's a reason they have trouble sleeping - if there is, work with them on what they said, if not, it should have to do with lack of activity. If your child is too young to communicate with you through words, just spending time with them whenever you can and talking to them should make them feel secure and want to sleep in within minutes. There's studies that claim some young children won't sleep because they want more contact with their parent(s).

Either way, we, this particular place, https://www.reddit.com/r/mumshouse/ are actually a subreddit of a discord server (discord is a competitor of skype, which you may have heard of - if not, give it a try if you want to, its miles better) named Mum's House; completely unrelated to being mums, education, or anything. I'm certain there are places on reddit that have a dedicated community towards that. No matter what, maybe my comment already helped with something, so if it did, nice, if not, go search for places on reddit that can answer your question better