FTM can feel kicks or movements as early as 18 weeks some don't feel until later. Depends on your size and baby position. Anything is possible, my father in law is a twin but was hiding behind his brother. So they didn't know.
And I'm 21 weeks of gone through three ultrasounds they should've known there no more than one at 10 weeks tbecause they would come from hiding behind each other cause they are too big at 10 weeks
You can only have twins if they are fraternal twins and has to be on your mom side if any fraternal twins are on your dad side you can't have twins