Q: If you go to a friends house that you visit very regularly, and bring a food item for yourself to snack on while you are there, are you obligated to offer it to everyone who lives in the house? Please provide me with detail and different scenarios in which this answer may vary. Also, if you live in the house and buy a food item for yourself, are you obligated to share it with the other members of the household?
A: If you take a food item when visiting yes, the expectation is that you would share it unless your hostess has said specifically that you should bring your own lunch or snack or whatever. Even then, you might offer to share with your hostess.
The answer to your second question really depends on your living agreement. If the agreement is that you live there but provide your own food, then it is your own food and you aren’t obliged to offer it up to everyone else. If the ethic is, instead, that you all share whatever you have, and you partake of others’ offerings, then you would indeed share whatever you bring into the mix.