It appears when the couple is mated if I remember correctly, it doesn't have to be a fated one. But it only works for omega and alpha couple.
Ive already asked the same question before and someone kindly explained it to me, so "the marks doesn't mean that they are fated mate or something like that, but when the one they love loves them back, it'll be a clear and unique mark, the same as the person they love and loves them back" (⌒▽⌒)
I believe the markings are actually confusing and not 100% worked out. The mark will only work between omega and alpha couples. In the case of Kalmen, Colton’s dad, he also had his mark become something but only with Colton’s mother. It was mentioned that she was his one and only. So it always confused me about Dylan. Dylan is actually mentally unwell and not just obsessed. Kalmen too.
just starting this one and I don't get those marks (?) they have on the shoulders, stomach, neck and so on. At first I thought they were scratches or burn scars but after seeing Colton's parents with leaves(?) drawn on theirs I assume it's some kind of destiny mark? like a mlp cutie mark idk does some design appear on it after becoming mates or smth?