I've never seen THAT before :huh: -- but it surely is precious! :rolleyes:
I have a cat who has a "nervous tic" and when he gets stressed out, he WASHES himself, and has at times through the years, licked his stomach till it looked SHAVED... but from what I can tell, watching, he's not "suckling" he's just WASHING...
I had another "rescue" at one point who was a "woolsucker" and she destoryed many afghans, blankets and comforters, when I would leave her alone to go to work. But since you are THERE (obvious since you were taking photos) I'm kinda surprised they aren't doing that to the insides of your arms, near your elbows, or something like that.
From seeing how WET his little tummy is, it's obvious they are BOTH slobbering like crazy, when they suckle... so it doesn't strike me as a "nervous" behavior.
I'm not sure how you can stop them from this behavior, unless possibly you get some "kitty formula" and give it to them in a "kitten bottle" -- but actually, they almost look too large for that to work.
Hope you can get an INFORMED opinion from someone on here -- but either way -- I still say the photos where they are BOTH doing it, TOGETHER... is SWEET... right or wrong... it's CUTE...