Missing numbers when counting

[3bunnies]

Not worried as much as curious why some of my dc consistently leave out some numbers when counting. Dd2 always left out 8 when counting to 10, then once she mastered that she would leave out 16 when counting to 20. Ds(4) is the same. He always leaves out 15 - this is when counting by rote or counting objects 1to1 and in both English(mother tongue) and French (dh family is French but ds only speaks a little). Why do/ did they do that. I know he won't go to secondary school ignoring 15, so I'm not too concerned. He will grudgingly add it in when prompted but it is as if it doesn't exist for him.

My DD has your DD's 8. She goes 1, 2, 3, 8!!! Or similar. The last number of a series is always 8. She likes 8, maybe your DD doesn't.

DD1 left out 2 for ages. Then I realised why.
When we went down steps we'd take it in turn to say a number:
Her: One
Me: Two
Her: Three... At that point she'd often join in with me and say the other numbers.

ds always misses 15, it drives me mad!

I have a friend who works in nursery with preschool children and she says it is quite common for children to get confused or skip numbers when they get to 14, 15, 16 when counting, not in age of course

16 was ds1's number block. But he'd then happily count on to twenty and beyond. He just didn't clock 16 for ages, not until he went to school reception really.

Yup 16 was DS' block until he went to school.
I spent a year trying to convince him of the existence of this number. Within a week at school it had appeared in his counting!

It seems like a widespread problem then. It is always 15, in French or English, never any of the other numbers. Yet he can count beyond fairly easily, he gets stuck when the tens change but he is aware of that and stops to ask me e.g. 49 .... I say 50 then he is off again 51 52 etc. He just seems oblivious to the existence of 15. Maybe I need to set up more games involving 15!