I'll only offer advice to family members or friends when they themselves say they want to lose weight.
My brother is a personal trainer and would start in on my mom and I when he would come back into town. Note: my mom gained a lot of weight after my father divorced her.
The shit storm that would ensue when my brother came into town was horrible. He would talk to us like we were gaining weight to purposefully piss him off. The thing was, he had no idea how we ate on a day to day basis, nor did he know our exercise habits. He would get so angry at our weight that he started to not only mentally abuse us, he physically abused me (broke a chair I was sitting in once and sent me flying backwards because I wouldn't go on a walk with him because I was massively sick).
Eventually my mom lost weight, but she did it in a VERY unhealthy way b/c he would never actually teach her about how to lose weight, he'd just berate her for her current weight. She has incredibly unhealthy eating habits still.
My entire preteen-mid 20 years were ruined and my confidence was completely shot because, according to my can-do-no-wrong personal trainer brother, I would "never be loved by any guy if I didn't lose weight." It took me looking back at pictures from those years to see that I was a fucking healthy weight! I had a bit of a pooch, but nothing I couldn't work off as I was very active at the time. I am SO mad at him for making me think I was "fat" all those years and it's the best I ever looked. I should have been enjoying my body, not hating it. I still struggle to love myself.
My brother and I no longer talk. I've learned so many positive, healthy ways to lose weight and be happy since (and met a gorgeous guy who loves my body and still wanted to marry me with a bit of weight put on).
I lost almost all of my respect for personal trainers because I see them treat people like my brother did. Groups/subs like this place (and /fitness, /progresspics, etc.) have helped A LOT too. Good for you for not doing to people what my brother did to us.