These are good questions. In my stories I've always been of the opinion that the Hutt's see their Kankhees as little more than pleasurable vessels for their heirs. The mother's would provide milk for their Huttese offspring for a week or two but then the child would be shipped off to Nal Hutta to be raised with the other Huttlings. Hutt's see humanoids as inferior so they would never allow them to raise their children. To answer your second question, have you seen the stone relief Jabba has on his sail barge? It is a carving of Jabba lounging with a number of his slaves around him. I imagine that Jabba has this carving to commemorate all of his previous Kankees and each time he takes a new breeder a new relief is made. Jabba also follows the old Huttese belief that all of his Kankhees will serve him in the afterlife. Hopefully that answers your questions but let me know if you have any others.
Yes, in my universe Rotta's mother was one of Jabba's concubines. I'm not sure yet who it should be but I kinda of want it to be someone significant in the Star Wars Universe