Does touching one's penis without sexual lust invalidate Wudhoo’ (ablution)? Does kissing one's young sister invalidate Wudhoo’?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The majority of scholars ruled that touching one's penis invalidates Wudhoo’, whether one does so lustfully or not. Busrah bint Safwaan narrated that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: "Whoever touched his penis does not pray until he performs Wudhoo’." [Abu Daawood, An-Nasaa’i, At-Tirmithi, Ibn Maajah, Maalik and Ahmad]

Abu Hurayrah narrated that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: "Whoever touched his penis with his hand with no barrier in between, then Wudhoo’ is obligatory." [Ahmad, Ibn Hibbaan and Al-Haakim]

Kissing one's young sister does not invalidate Wudhoo’ unless it is done with sexual lust. In Al-Mughni, Ibn Qudaamah said: "Wudhoo’ is due when one kisses out of sexual lust, not out of compassion."