Complex sentence: His uncle soon discovered that Hamilton had a remarkable ability to learn languages, and from a young age, had displayed an uncanny ability to acquire them (although this is disputed by some historians, who claim he had only a very basic understanding of them).
Split into simpler sentences: His uncle soon discovered that Hamilton had a remarkable ability to learn languages. At a young age, Hamilton displayed an uncanny ability to acquire languages (although this is disputed by some historians, who claim he had only a very basic understanding of them).