在Ａ裏 is indeed used a lot in Chinese, for example, 在這個家裡﹐每個人都必須做家務事。不然的話﹐家裡就會亂七八糟. Namely, in this family everyone must do housework, otherwise the house would look chaotic. For another example, 在一群人中﹐不能沒有友情。沒了友情﹐這群人就會散去。 Among a bunch of people there must be friendship, otherwise they would go their own way and would not stay together. As we see, 在Ａ裏 can mean in A, among A, within A, and so on. Your translation shows that you have already understood 在Ａ裏 quite well. 在Ａ裏 basically provides the stage for events to happen, affairs to unfold, people to do things, and the sort. Putting 在Ａ裏 at the beginning of the sentence is to emphasize the stage: In this world, in this family, among this group of people, and so on.