Birthmarks can appear after birth, making the term technically a misnomer in these instances. But still, that same cafe au lait type of mark, for example, can appear after your well into adulthood.
Yes, they can. I have two birthmarks that appeared after birth. One is on my knee and appeared when I was about 7 years old. The other one is on my left arm and appeared after I went tanning for the first time. I was too pale to see it!
Birthmarks are by definition a mark that is apparent at birth. All other features that appear to be birthmarks ought to be known by a different name, either scars, blemishes or another word. People do sometimes call marks of a certain type birthmarks, and while it may make sense it is not technically correct.
my name is Tasha and im saying yeah they can i was never born with a birth mark but when i was 9 a bullet sized brown mark appeared on my ankle and now one that i just noticed has appeared in between my legs on my right cheek.