my child; my son
Humble term used to refer to one's own child, especially a son, when speaking to others. Conveys modesty by literally meaning 'pig child'. Not used for others' children.
piglet
Rare literal meaning; almost never used in modern Japanese outside of historical or literary contexts. The humble sense is overwhelmingly more common.
My son is always in your care.
Thank you for attending my child's school entrance ceremony.
In old texts, 豚児 can literally refer to a piglet.