exclude

How many times have you forgotten, to include everyone, when you sent your wishes/invite on important events?

Did you forget who they were dating, if single ? or just one and forgot to mention the other ?

Did you mention only thier dates and forgot thier family ? Together is it you can or you may ?
( 'can' applies to what is possible and 'may' applies to what is permissible)

What if it is intentional blanking out of the rest, by a person who follows etiquette  to  great extent due to insecurity?

Sure, response could be  a dead silence of 'you deserve it'  followed by, if they are genuine ones who care,
'are you really that busy?' later.

If you really forgot , then it is usually numerous sending of the same message, multiple times addressed to each indivisual related to the family.

Derek says 'You can't please everyone in this world.'