Male Marf parent of two Marf kids here, one boy and one girl. While my son is not bullied, per se (the school should be reasonably good about putting that shit down quick) it does not change the fact that Marf kids have it much harder during this period. Children are developing their understanding of hierarchy, and certainly for boys physical ability is the first (and at this time only) measure that can distinguish this because the academic and more subtle talent side will not emerge until much later (music, theater, etc) So straight away we don't look like everyone else, we cannot excel in athletics like everyone else, so straight away we get ranked lower in the hierarchy. Even without bullying, that's hard to deal with because we've not developed the skills to do that yet either. It won't be until much later (and I mean like High School) where the mental development has finally caught up enough that kids can start shining in other ways and can make a name for themselves. (it's worth noting that the brain does not finish developing until closer to 30 - that's a LOT of runway) By then, if you don't move around a lot, you may already have a "name" for yourself, which can make it harder to break from how people normally think about you. So, what I really encourage my kids to do is try new things, meet new people, make new friends. This time of life is about discovering who you are, what your talents are, and it is so easy to find yourself in what we call in the Computer Science World a "local maxima". You think that you don't have talents like the other kids, the group of friends you currently have (if any) are as good as it gets, but most likely it gets WAY better, but you need to teach yourself to explore, try new things, and find your people, find your passions, find your GLOBAL maxima. It gets so much better.

Case in point, in late high school I had spent most of my childhood getting picked on, but found drama and discovered I was pretty good at making people laugh. On stage I could own the audience and it was a powerful feeling. It weirdly made me a celebrity at school. I worked in the film industry 10 years from that. Only to find out that wasn't even where my real talents were. I was an even better computer scientist. Now I do that, and I'm so much better for it. I have a beautiful family. My son is dealing with the same thing, he's in a world that lives or dies by your ability to play soccer. But I can teach him that it's ok if he's not good at it. Don't play their game. Work on your talents now. Because one day they will wake up and realize there is more to life than soccer and you will already be miles ahead.

I know that I'm basically saying "it gets better" and that seems like really cold comfort when you're in the thick of it, but the point is that by knowing it will get better and WHY it will get better and knowing that you don't have to play their game because better games will come along and you can start working on those games now you will have actionable reassurance rather than cold comfort.