Tell your family about the four regulative principles and why one should follow them. Initially there may be some resistance, but if you are strong and pure, it will go away. Or you can introduce them to some senior devotees who might be able to convince them. You can pray to the Lord for their upliftment.
Especially in the month of Damodar and Purushottam, it is recommended to be vegetarian. Hopefully you can convince them, other wise you have to cook yourself.
GM approved reply/05102020