Is it possible??🤔😬

I had my first ultrasound when I was 5 weeks and I go back for another one at 9 weeks. Is it possible to not see twins but when you go back for another ultrasound it turns out to be twins?? Twins run in my family and I kinda want twins! I think it would be so cool. Just wanting to know if anyone had any stories on how they found out about their twins!😊🤞🏻