What is the ruling on a man's brother's and sister's children kissing and hugging their paternal uncle's wife, and what does the wife's statement "my sister's son has a beautiful face" mean?

Kissing between unmarriageable kin (mahārim) is permissible if there is no fear of temptation (fitnah) and no lust. This should be on the forehead or head, not on the mouth, such as someone returning from a journey kissing his female mahārim, or a brother kissing his sister, or a father kissing his daughter. There are narrations that indicate this. However, if a husband forbids his wife from kissing her mahārim, she must obey him.