Northeast US: Laws regarding parents buying their kids alcohol?

So basically I have a paper to do about legality of parents purchasing alcohol for their kids. I am wondering if it is legal for a parent to buy liquor/beer at a store, and bring it home for their kids to drink (I found some info saying this is fine)....Also, can parents buy drinks for their kids while eating at restaurants? I'm not talking about getting drunk here, but more-so having a drink or two with the family. Also, when I say kids, I mean at least above the age of 16. I am looking for either cited sources, or perhaps information from somebody with bar tending, restaurant management, or law enforcement background. Thanks a lot for the help.