My 13 month old isn't walking yet. Isn't that really late?

Doubt it. I like to see a kid get themself to sitting by 9 m, pull to stand/cruise by a year and walk independently by 15m. If premi, I adjust my expectations accordingly. (1 month premi gets an extra month to do it) Review this with your doc.
No. As long as your child is otherwise developing normally, this can occur. Your child should be able to pull them self to stand, walk with assistance, and cruise.