What is the expiation for someone who fondled his wife during the daytime in Ramadan and unintentionally inserted a small part of his penis into her, and what is due upon him and upon his wife?

A fasting person must avoid everything that arouses their desires; because indulging in foreplay may lead to invalidating the fast. Many scholars disliked kissing for those whose desires are aroused. If what entered was a small part, less than the glans, then the fast is valid if no maniy (seminal fluid) was discharged. As for her, some scholars believe her fast is invalidated due to something entering her interior. As for inserting the glans or its equivalent, it invalidates the fast of both individuals, requiring qada' (making up the fast) and kaffarah (definition) (expiation) if done intentionally. They differed concerning forgetfulness.