Welcome to the forum, Frizzy!
Sometimes comments are cruel because people don't think about what they're saying. Other times it's because we read too much into them ("She's saying I look fantastic? Does that mean I looked like crap before???"). Other times it's because people are deliberately trying to be cruel, like in the case with the bulimia comment.
I understand that it can be hurtful and annoying, but I always feel pity for people whose only method of building themselves up is by knocking others down. If your family are all heavy then the negative comments could come from jealousy. Or maybe from denial. They desperately want to believe it's genetic and that they can't lose weight. You share the same genetics yet here you are proving that sensible eating and exercise can make you lose weight. This attacks their own sense of identity and puts responsibility for their weight back on them. They either have to accept that they're overweight through bad food choices and lack of exercise, or they can continue to believe that it's all genetic by pretending you're not losing weight in a healthy way. If they convince themselves that you are losing weight in an unhealthy manner, they can continue to fool themselves into thinking they're being healthier by staying overweight. My family does the same thing so I know of what I speak!
There's nothing wrong with wanting to get to the lower end of your healthy BMI range. People have different builds and different healthy weight points. Some people would look fine at BMI 25 but gaunt at BMI 21. Others would feel overweight at 25 but would feel brilliant at 20. It comes down to the individual. I'm hoping to eventually get to my lower BMI range because my family has a history of joint problems. But given how hard it's been to shift these last few kilos to get to BMI 25 I don't know how long that will take!
Congratulations on your weight loss so far, and good luck with the next stage of your weight loss journey!