Does the latter invalidate wudoo’ in the case of a married couple?.
A man and his fiancée are not married, rather she is still a “stranger” (non-mahram) to him until the marriage contract is completed. Based on this, it is not permissible for him to be alone with her or to travel with her, or to touch her or kiss her. No one should take this matter lightly, because the Prophet (peace and blessings of Allaah be upon him) said: “If one of you were to be stabbed in the head with a needle of iron, that would be better for him than touching a woman who is not permissible for him.” Narrated by al-Tabaraani from the hadeeth of Ma’qil ibn Yasaar (may Allaah be pleased with him); classed as saheeh by al-Albaani in Saheeh al-Jaami (5045).
Concerning the ruling on touching one’s fiancée or being alone with her, al-Zayla’i (may Allaah have mercy on him) said: It is not permissible for him to touch her face or hands – even if there is no fear of desire – because she is still haraam for him and there is no need for that. End quote from Radd al-Muhtaar ‘ala al-Durr al-Mukhtaar (5/237).
Ibn Qudaamah said: It is not permissible for him to be alone with her because she is still forbidden, and Islam does not allow anything but looking, so she remains forbidden for him. And because if he is alone with her there is no guarantee that something haraam will not happen. The Prophet (peace and blessings of Allaah be upon him) said: “No man is alone with a woman but the Shaytaan is the third one present.” And he should not look at her with pleasure and desire, or in a dubious manner. End quote.
The Messenger (peace and blessings of Allaah be upon him) warned us against being alone with a non-mahram woman, and said: “No man is alone with a woman but the shaytaan is the third one present.” Narrated by Ahmad, al-Tirmidhi and al-Haakim; classed as saheeh by al-Albaani in Saheeh al-Jaami’ (2546).
With regard to the greater purification (ghusl) being required because of kissing, that is not the case. Rather the greater purification is required if maniy (semen) is emitted or if intercourse takes place. This has been discussed in the answer to question no. 7529.
With regard to wudoo’ being broken by touching a woman, this has been discussed in question no. 2178.
And Allaah knows best.