Praise be to Allah.
The scholars (may Allah have mercy on them) differed as to whether touching the penis invalidates wudoo’ or not. This has been discussed previously in the answer to question 82759. The most correct view is that if the touching is done with desire, it invalidates wudoo’.
If a woman touches her husband’s penis with desire, it invalidates her wudoo’, but if it is without desire, then it does not invalidate it.
‘Ulaysh said in Minah al-Jaleel Sharh Mukhtasar Khaleel (1/113): The ruling on touching the penis of another person depends on whether it was done deliberately or whether accompanied by desire. End quote.
If we say that it does invalidate wudoo’, that is on condition that there is no barrier. This is the view of the majority. So if a woman touches her husband’s penis with a barrier, her wudoo’ is not invalidated, even if it is with desire, because of the report narrated by Abu Hurayrah (may Allah be pleased with him), according to which the Prophet (blessings and peace of Allah be upon him) said: “If one of you touches his private parts, with no barrier in between, then let him do wudoo’.” Narrated by ash-Shaafa‘i in his Musnad, 1/12; classed as saheeh by Shaykh al-Albaani in Saheeh al-Jaami‘.
See also: Haashiyat as-Dasooqi, 1/120; Mughni al-Muhtaaj, 1/1.2); Mataalib Ooli an-Nuha, 1/143
If a man shakes hands with his wife or kisses her, or she kisses him, that does not invalidate the wudoo’ of either of them, even if it is done with desire, so long as nothing is emitted. That is because of the report narrated by ‘Aa’ishah (may Allah be pleased with her), according to which the Prophet (blessings and peace of Allah be upon him) kissed one of his wives, then went out to pray and did not do wudoo’. Narrated by at-Tirmidhi, 86; an-Nasaa’i, 1/104; Ibn Maajah, 502
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him) said: … The correct scholarly view is that it does not invalidate wudoo’ at all. If man touches his wife or kisses her, it does not invalidate his wudoo’ according to the most correct opinion, because the Messenger (blessings and peace of Allah be upon him) kissed one of his wives, then he prayed and did not do wudoo’. Also, the basic principle is that wudoo’ and purity (tahaarah) remain intact, and it is not permissible to say that it has been invalidated by something unless there is proof to that effect, with no counterproof. In this case there is no proof to indicate that wudoo’ is invalidated by touching one’s wife at all.
End quote from Majmoo‘ al-Fataawa, 17/219
And Allah knows best.