Family issue

Gud mrng frnds today I wanna share a prsnl prblm and pllzz suggest me tips in sorting out this problem . My mom and dad have been married for 25 yrs since past 8 months he is talking to colleague of his sooo closely to such an extent that my dad daily sends gud mrng love u sweet heart darling msgs to her in whatsapp but recently 3 months my mom came to knw abut this affair we informed to our family members but thr is no result bcz wen v say anything he always uses the word I will die . my mom loves him alot & is not at all ready to give him divorce. Bcz once she issues divorce he will go start enjoying wth tht lady openly. He is irritating n torturing us daily. Wat can v do to get him back .