Once I had to spend a week with DT1 at my mother's, whilst DH went with DT2 to my in-law's. When I returned, I had DT1 in a single buggy and DH met me at the airport with DT2 also in a single buggy. As we walked to the car, the twins reached out their hands to each other and held them, looking at each other. They were so happy to see each other, it was a heartswelling moment for me.
My twins don't yet play with each other much (they are 2 years old), but occasionally they will invent a "game" that puts them in hysterics. One is where each sits on an arm of the sofa, so they face each other. They clap their hands whilst going "la-la-la" to each other, and then both throw themselves onto the sofa in a fit of giggles.
When one is crying, the other will often go and get their favourite soft toy from their cot, and give it to them.
I'm not going to dwell on the fact that they fight with each other....
One DT tells the other off, which is most amusing. This was particularly great when it related to food the other DT had dropped on the floor. I thought, "exactly!".
An advantage of twins is that you can see more clearly when some aspect of childrearing isn't your fault; for example, when one twin eats well, and the other doesn't, you know the badly-eating twin's habits are not down to you!
All the best with your pregnancy Anjlix,