Can a 25 year old son-in-law hug his 58 year old mother-in-law?

A son-in-law is a Mahram to his mother-in-law and there is no observance of Hijaab between them. It is also important to point out that if the son-in-law or mother-in-law experiences passion while hugging one another, that will fall in the category of incest which will result in her daughter’s marriage being invalidated. It is, therefore, important for the mother-in-law and son-in-law to conduct themselves in a modest way.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai