Poojas to perform for the soul to rest in peace - Opinion needed.

My FIL passed away last December and my DH being the eldest did not perform any prayers after his passing. My FIL left the family 30 years ago and married another woman. His children from the second wife did all the rituals. Before he passed, FIL wanted to see his children from his first wife but they refused to see him.

Recently my family has been facing a lot problem and bad lucks. We consulted a sami and he told us that my FIL's soul cursed our family as his soul was not a peace since his eldest son did not perform the death rituals.

I don't know if I could believe this. My DH seems to believe it since he is the one facing a lot of problem lately.

I would appreciate if anyone could enlighten me on this matter. Most people we consulted are more keen to earn money from the various pooja's that they suggest we perform to ward off the curse.