Late to all gross motor milestones - looking advice/reassurance

[bouncingblob]

DS met gross motor milestones as follows:

Rolling - 6 months

Crawling - 9 months caterpillar (13 months before on all fours)

Sitting up independently - 10 months (11 before he could get in/out of this position himself)

Pulling to stand and cruising - 15 months

He's 16 months now and not independently walking.

Once he hits the milestones he is great at them. But why are they all so late? Has anyone else been through this?

Fine motor skills are excellent. Comprehension is excellent even if vocabulary isn't but we're not worried about that. Socially we have no worries about his development.

Sounds like my second, won all his races at sports day a couple of weeks ago! Walked at 18 months, DC1 only walked at 17 months. Honestly after a few weeks I couldn't tell a difference between my DC and their friends who had been walking for 6+ months more.