It seems natural and appropriate for an older man to call a non-relative boy/young man “son” to convey endearment. Although I’m not sure, I think it’s unofficially reserved for men’s use only (the older person is male).
However, if he younger person was female, “daughter” seems awkward.
Is there a analogous term of endearment for young females? If so, it is reserved for older women’s use? Or is “daughter” used?