Reference: Liqaa.aat al-Baab al-Maftooh – Volume 1, Page 27, Number 39
Question: Does touching the penis with the hand nullify the wudhoo?
Response: The predominant opinion according to me is that touching the private parts does not nullify the wudhoo unless it was done with desire, in which case it nullifies the wudhoo. And if someone else [touched the private parts], then it is the same [ruling]. Based upon this, the wudhoo of a woman who cleans a small child’s private parts is not nullified.