Lost an identical twin at 7 weeks :(

We were soo surprised a couple weeks ago to find out we were having identical twins from our one IVF embryo. After the shock..we got super excited and started to be absolutely in love with the idea! today at our 8 week ultrasound we found out one twin no longer has a heartbeat and stopped growing 5 days ago. The other one looked great. the doc is concerned that since they are identical they have the same genes..there is a chance, if they are not genetically sound, that I will lose the second one too. Luckily they both had their own sacs. I am so upset about losing the one, but trying to remain hopeful that the other one grows strong! Anyone ever been through this? any insights??