What is the ruling on an unmarried woman suckling children she is not breastfeeding, and will that affect her breasts in the future?

The act is permissible as long as it does not lead to a forbidden outcome such as gratification, arousal of desire, or the exposure of nakedness before someone to whom it is not lawful to look. If there is no milk in the breast, then no prohibition of suckling results from it. It is recommended to avoid this act and use other means to quiet the infant.