For my child (peri tou emou teknou). Tender and affectionate reference to Onesimus as his spiritual child.
Whom I have begotten in my bonds (hon egennēsa en tois desmois). First aorist active indicative of gennaō, to beget. See note on 1Co 4:15 for this figurative sense. Paul is evidently proud of winning Onesimus to Christ though a prisoner himself.