I can go either way on this one, but, all in all, I think a suckling kitty is rather cute. And, yes, by the way, I think suckling pups are cute too
None of my current cats (or dogs) suckle, but I've had a couple of cats in the past that did suckle and I always thought it was a sweet sentiment usually reserved for those they were especially bonded to. Opal was my siamese mix and she was the resident suckler. She was rescued from death row at a high-kill shelter at under 4 weeks of age. I was only a teenager at the time (13 years old), but I bottle-fed her until she was able to be weaned onto kibble and wet food. Both before and after her feedings, we would snuggle on my bed and she would suckle on my fingers and knead at the hairline at the back of my neck. It was very sweet and it was a behavior she kept long after her weaning days were over. And, in fact, it was the fact that she stopped that behavior that I knew that she was ill. Unfortunately, I lost her about 6 years ago. She was only 7 years old, but succumbed to cancer. She was my girl and I still love and miss her to this day
As much as Opal's suckling was sweet, Zeus' suckling was not. Zeus was a female (yes, female
!) cat who had to suckle in order to comfort herself. And she suckled a lot. All. The. Time. It was sweet at first, but as time grew on and she became more neurotic, her suckling became less sweet and more aggressive and obsessive. She would pin your arm down with her claws and bite and suckle on your fingers. It became so bad that I would have claw marks up and down my arms and swollen, bruised fingers from the force in which she suckled. She also had a tendency to suckle on bedding, pillows, and clothing and I lost many an item to holes in the fabric caused by her intense suckling. Zeus was not my cat, but rather my mother's boyfriend's cat, and I didn't know much of her history, but she had some severe issues and was also prone to over-grooming and separation anxiety. I was her main caregiver (as well as caregiver to all our pets) as my family had proven not to be particularly caring and conscientous. And, while I did grow to love Zeus, she passed away at a young age to liver failure
(she was poisoned as she became an indoor/outdoor cat following my moving out on my own). She was a sweet cat, but her suckling was too aggressive for my tastes and was often destructive. But, then again, she needed to suckle in order to feel good and that, in and of itself, was the issue since she learned no other self-soothing methods. The suckling was a behavior she relied on and she struggled with anxiety if unable to practice the behavior.
So, that's where my stance with suckling is. I think it's an okay, albeit even sweet, behavior if it's not the only behavior a kitty has in its arsenal to provide comfort and stimulation for itself. In some situations it can be a sign of bonding, but in others, my opinion is that it can be destructive -- both physically and emotionally for all involved.