Twin pregnancy question??

Evelyn • I am 32 yrs old. With my DH for 10 years. TTC #3
I'm currently 7 weeks but I had a sono at 6 weeks and there were two little beans in there. One was larger than the other and had a heart beat. The tech said the other one might have been implanted at a later time. Has this happened to anyone else. I go back next Tuesday at my 8th week and I'm nervous to hear the other heartbeat. 😰