What is the ruling regarding the prayer of a woman whose son kisses her while she is praying, unintentionally? Is her prayer invalidated?

Kissing a child during prayer may fall under the category of a minor action that does not invalidate the prayer. This is determined by custom. If people consider the action minor and not contrary to prayer, then it does no harm. The Prophet, peace and blessings be upon him, carried a child while he was praying, which indicates the permissibility of such minor movements. Likewise, a minor action is not disliked if done forgetfully.