Bit of a mess, isn't it, that area... the trouble is they're probably Ilex aquifolium, and they get very large indeed. Those saplings are way too close to one another for each one to be shaped in any way, really. I suggest you either take some out to make more space between them and prune the remainder back (if you don't mind the thought of 12-15 feet high dark leaves all year), or alternatively, keep them all at a certain height to create more of a wild hedge appearance. Either that or remove them altogether, info on the plant here https://www.rhs.org.uk/Plants/9087/Ilex-aquifolium/Details
Whatever you decide to do, protective clothing and safety glasses are a must...