When we got the kitten she was 6 weeks old & the dog was having a phantom pregnancy. The kitten liked to suckle from the dog & the dog loved her new baby & washed her & encouraged her to keep suckling. At first it was cute, but the phantom went on & on & on & on, pretty much until her next season (when she was mated anyway) We tried & tried & tried to discourage her, but still she carried on.

The dog went away to stay with some friends for 6 weeks at one point (not because of the cat) but we thought that would stop her for good. BUT the dog came back, the cat went bonkers that her buddy was home & started again.
She's now 2 and a half & still does it, they have a lovely close relationship & although it's a bit weird, it doesn't do either of them any harm.