Is a boy of 15 years old allowed to kiss and hug his grandmother
Is there a source to be machmir stringent.
Yes he is allowed, the same way it is permitted for a father to kiss and hug his daughter. The reason is because it is being done out of closeness, and not because of gender attraction. The same applies to a girl with her grandfather. There is a source that says not to, (Ran) but that is not the way the poskim pasken. Additionally see Otzar Haposkim E:H 21-6 regarding opinions that even the Ran permits it). I am not aware of sources in the poskim that are stringent. As a side point all of this is only when it is being done out of family closeness and not with unclean thoughts
Bach E:H 21-5, Chelkas Mechokek E:H 21-10, Bais Shemuel E:H 21-14, Piskei Teshuva E:H 21-5, Chochmas Adom 125-6. (See Igros Moshe E:H 1-60, regarding a man kissing his son’s daughter, however that would not apply in this instance.)