my family used to be all pescatarian, then vegetarian- and were for about 15 years- but then my dad succumed to the lure of the bacon buttie and the chicken balti, and went back to the darkside about 10 years ago.
we're probably pretty unusual as to why we went first pescatarian, then veg. when i was 4 my throat and mouth started swelling up really impressively whenever i ate meat, and my doctor said it could be anything from colourings to preservatives to 'who-knows-what they put in british meat in the 1980's', but that it'd be most practical/easiest to just not give me meat again, so we didn't.
my dad used to itch whenever he ate anything with animal fat in it anyway, so it was no skin off his nose, (and he's always said that my mum was/is rubbish at cooking, and it was one less thing she could accidently poison him with) and my mum thought it was one less expensive food item to pay out for and to mess about with in the kitchen. my little bro was a baby so he just never even got started on it- and he's the one who questioned our eating of fish as a small child (we had some as pets) and shoved everyone over the edge to veg.
so my dad eats meat again now *grrr*, but the rest of us have a good few years of veggie behind each of us (my bro and i are all grown up now!), and are still going strong- i quit eating eggs, dairy and honey years ago, and my mum is now dairy free and down to about one egg a month, since i suggested that it would probably dramatically affect her sinusitis and tummy troubles- which it did (yey!).
i think it made it a lot easier that we were all veggie, in that nobody had to worry about what they fed anyone else, make multiple/variations on meals, or risk contamination (till i quit dairy and eggs).
we found it hard when my dad went back to eating meat though, because the whole dynamic changed, my mum or he had to cook his gross stuff (me and my bro shuddered at it, and had no clue how to, even if we wanted to- which we didn't) and we hated the new meaty pans, meat in the fridge/on the stove, the horrible smells, etc, that were totally alien and gross to us.
i'm also lucky that there were always a few other kids with veggie families in my school classes, and that the UK was/is veggie friendly- it always just seemed pretty normal, maybe a little unusual at most, but never weird, that we didn't eat meat in our house.