If the son-in-law is a mensch he will understand the father-in-law’s concerns and be grateful for his help.
You mean that if he is a mentch he will thank his mother-in-law for her “concern” that he might get divorced in the future and that she is “only” protecting her family from him to insure the best financial outcome for her post-divorce daughter, and so he will effusively thank her for making sure that he has no title to the home that he is expected to pay the mortgage for and further be grateful to her for thinking of his wife’s future once she potentially gets divorced from him?