If I recall correctly (And if we're talking about the vocaloids here), Oliver is voiced by some (atthetime) 12-year old chorus boy (and is kept anonymous for that reason), and if you're talking about Kagamine Len, he was voiced by a female.
If you're out after the shonen voice as utaforum forces me to call it, then I'd reckon those are rare, even in a badly made CV form, simply due to the fact that all the young boys are off playing on their fortnites or getting groomed by some sussy individual instead of making UTAUs, and for the female doing the shonen voice part, they're most likely primarily japanese.
Yeah, no, this ain't helping, but I felt I had to explain that finding the voice of a young male or an impersonation of it is... Difficult, and a solid English voicebank even more so, if not staight up impossible, except for the paid options.
What you decide to do with this information is up to you, but if it is, indeed, young boy voice you're after, I've got nothing else than to obtain vocaloid, the means I'll leave up to you.
While I could not help with your predicament, I still believe this information is useful to keep in mind.
If you simply want less deep voices than manly gruff, go look for voices in the
tenor range, as tenor is the highest male chest voice type (meaning, normal speaking and whatnot), as I have little doubt that there are plenty of tenor voices to choose from.
To summarize:
Oliver and Len
(kagamine) are voiced by an unidentified choir boy and a female voice actor respectively, and so finding a solid english voicebank for this vocal range I will theorize is an extremely rare and difficult, if not currently impossible process, so my only knowledge is to obtain vocaloid, keep digging deeper and risk finding nothing, or settle for a tenor range voicebank.
Edit: I now learned that this forum does, indeed, have a word filter that replaces words.
