Kittens suckling eachother

I was at the vet's office today and they had 4 kittens in a cage up front. They always have kittens in this cage that are up for adoption. Anyway, 3 of the kittens were trying to nurse on the fourth kitten. Poor kitten kept getting up and moving but they wouldn't leave the poor thing alone. So I opened the cage and took out the one. Her little belly was wet from the "nursing". I held her until she cleaned and straightened her fur back down. Then I played with her for a while. The nurse must have thought I was crazy since I wasn't even there with an animal of mine. I just happened to be walking by on the way to the grocery store a few stores down and saw the kittens in the window.
They were out of water too! I told he receptionist and whe said "Oh they knock the water out all the time" Poor kittens were tying to drink from the bowl. It was all I could do not to get the bowl out and take it somewhere to fill it up myself.
I put the kittens back in the cage. They did not try to nurse on the one anymore. I was real happy about that. I went to the grocery store. I decided to go back by the window to see if the kittens had water yet. Well they didn't, so through the glass I motioned to a vet tech, who I am familiar with. He is great! I pointed to the dish and he saw that they were out of water. I motioned thanks to him and went along my way.

So...after all that, I have a question...Is is safe, good, bad, indifferent for kittens to suckle and nurse on one another??? It just looked unnatural to me and it looked uncomfortable for the one kitten that as being nursed on.

Awwww..the poor babies were needing to be nurtured. They will do this when scared or in need of comforting. So, it is not unusual, but it does indicate that they need loving. I wonder whether they were taken from their momma too early???