Junk food baby

So I’m from Oklahoma , where we’re not really progressive at all . Even though I do live in the city . But how do you keep your child from eating junk food when everyone around them is eating it and your child sees and wants it . My baby is only 5 months old right now but they’ve already stuck cake in his mouth after I told them he wouldn’t be eating sweets when he’s older . Then my boyfriends side of the family kept touching meat and pizza and sticking their fingers in his mouth after I told them he’s gonna be a vegetarian like (also tried sticking pizza in his mouth)

My boyfriend also has a two year old daughter , which her parents ( her mom and stepdad) always bring her here with McDonald’s chicken nuggets even when she was one. So we try to give her healthy food here . (She is twice the size of her 3 year old cousin ) But she won’t eat any vegetables now . Also she looks at her sippy cup and if it’s clear , she throws a fit because she doesn’t want water . ( they give her heavily dyed juices ) Around my boyfriends family , they all eat bad and constantly try to give her candy , cookies , cake and soda . Also if they eat it in front of her she wants it and won’t eat real food or if someone is drinking soda , she won’t drink her drink . So how do you keep your children healthy around unhealthy family . Cut them off or ? Plus they don’t respect anything we say .