Twin bond

As the babies get older I notice more of a bond between them. If one of them wakes up before the other I can hear grunts and shouts as if they are trying to wake the other one up. The other day at the store Ashley was pushing Lily and I was pushing Preston in a separate buggy. We were on 2 different aisle but the babies keep calling back and forth all over the store. Lily would yell, then Preston back and forth until they saw each other again so they could crack up laughing at each other's sight. If one is is a different room then the other they look around as if they are looking for each other. Will this twin bond last? In my mind I picture them being bff's all their life. I am sure there will be bouts of fighting but right now I am enjoying the little bond they have.