Baby monkeys playing at Wuyishan

or comment on grooming unusual behavior, here is a review by a primatologist. Do for anyone curious about it, it is the answer:
It seems that adults are only grooming that child, not to stimulate urination, but only as part of the overall preparation.
You can see that more than one female is making motherhood behavior is common.
Usually the mother Real does not tolerate too much of that.