I used my fingers & flicked my lo's cheek since young.. Now lo doesn't bite anyone or put things in de mouth.. Until in childcare where they learn a few gd & bad things.. So far lo only been bitten by other children haha..
sounds like your younger boy is teething? first of, try to give him something else to chew, ice cubes helped my son. secondly, time out from play when he bites again - any one! π
This article should help https://sg.theasianparent.com/stop-child-biting π