What does Yuvan mean?
From Sanskrit yuvan (युवन्), 'young, youthful', and as a noun 'a youth, young man'; the dictionary sense also extends to 'strong, healthy'. A well-attested classical word.
What does Devansh mean?
A compound of Sanskrit देव (deva, 'god, divine') + अंश (aṃśa, 'portion, part'), read as 'a part/spark of God'. The elements are genuine Sanskrit, though the compound itself is a modern coinage used as a name rather than a classical term.