en_tn_condensed/pro/04/03.md

When I was a son of my father

This refers to the time when the writer was a child still living under his father's care. AT: "When I was still a boy learning from my father" (See: rc://en/ta/man/translate/figs-explicit)

the tender and only child

Here the word "tender" refers to a young age at which the child is still weak. It forms a hendiadys with the word "only." AT: "the tender only child" (See: rc://en/ta/man/translate/figs-hendiadys)