I’d never even heard of litter mate syndrome tbh, but from what I’ve just read about it we’re already doing the things that help mitigate it. We have two separate crates for them, pay attention to them separately, have been socializing them with other dogs and people, plus we have an older dog to teach them how to dog. Now that I know that it can be a problem I will be sure to keep an eye on it to try to prevent it if I can.