My parents are paying for the wedding-church, hall, flowers the whole thing in general. my fiancé’s parents are gifting us a large amount of money and also paying for rehearsal dinner and contributing to the photographer and flowers and decor...

It is embedded in my mother and fathers head that ONLY the brides parents should be on the invitation, is this true? I am Greek Orthodox if it makes any difference

I am dreading saying anything about it to my FMIL and his sister... I feel like this is going to be a family feud. His sister has been married twice so I can’t compare to hers.