It is good to hear about the 4 hedgehogs. It seems that suburban gardens are becoming more of a stronghold for them these days.
As WilliamC said, the hoglets do become independent when they are comparatively small. They will, though, sometimes congregate at feeding places and a lot of them seem to like sharing, but may not necessarily be from the same litter. The adults are often very tolerant of hoglets and one particular hoglet may share a feeding bowl with several different adults at different times, so it is not easy to tell which belongs to which hog. Is the bigger one definitely a mature adult? Because, the other possibility is that all 4 are youngsters, with one of them being an early hoglet and the others more recent.
Whatever their relationships, It is lovely that you have 4 hogs visiting. I hope you continue to enjoy watching them.