Does the ablution of a woman who cleans her son, or a doctor and a son who cleans his father, become nullified? And does any touch nullify ablution?

The ablution of a mother is invalidated by touching the penis of her child according to the Shafi'is and Hanbalis, and this is the opinion of many scholars, contrary to Dawud, who does not see ablution invalidated by touching the penis of another person absolutely, and contrary to some who do not see ablution invalidated by touching the private parts of a minor. They cite as evidence the general meaning of the hadith (definition): "Whoever touches the penis, let him perform ablution," and because touching the penis of another is more likely to incite lust and sin. As for the Hanafis, they do not see ablution invalidated by touching the private parts absolutely, citing as evidence the hadith of Talq ibn Ali: "It is merely a piece of you." Some scholars hold that the invalidation is conditioned on touching with lust, and this is an opinion among the Malikis and was chosen by Sheikh Ibn Uthaymeen, as a reconciliation between the hadiths. The ruling issued as fatwa (definition) is the opinion of the Shafi'is and Hanbalis that touching invalidates ablution absolutely.