According to the official position of our madhhab, skin-to-skin contact with the opposite gender nullifies wudu, with the exception of one who is not your permanently unmarriageable kin (mahram). The one who touches is like the one who is touched. [Touching] the young child who [according to custom] has not reached a stage of sexual interest, hair, teeth, and nails, does not nullify wudu, according to the more correct opinion. [Minhaj al-Talibin, 1/10]
Touching the skin of one’s spouse, if but a little, and whether intentionally or unintentionally, nullifies one’s wudu.
Answered by Shaykh Isa Husayn