Momo or modi

My ultrasound shows two sacs & we saw two babies but they are having me come in for another ultrasound next week to find out if there is a membrane between these babies. I’m trying to see if anyone has experience with this and if anyone knows what the chances of there being a membrane since there are two yolk sacs or does that even mean anything at all? I was told to absolutely not look at google & so far I haven’t but I’m so curious to know if anyone else has experienced this & If you had two sacs What type of twins did you have?