I'm vegan, and know enough about the consensus of the nutritional community to say a healthy vegan diet isn't lacking in any nutrient, and can provide health BENEFITS when it comes to certain things. That being said, I eat horribly, myself, so don't have many recommendations- it's a mistake to presume you must consume something that resembles animal products, though, which many people do. The "faux" meat, milk, etc is all optional.
Question....if animal protein makes you sick, to the point where you'd be facing abstaining from consuming it entirely,
why would your family have you eat it?
Did I misunderstand the original post?
Anyway, I agree with Mackica...if you cook healthful vegan meals routinely, and your brothers eat them, there may come one pivotal day where your dad's too tired to make something for himself, and tries a bit of your food and concedes it isn't horrible. 
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For there is another kind of violence, slower but just as deadly, destructive as the shot or the bomb in the night. This is the violence of institutions; indifference and inaction and slow decay.