i think probably the Rov would go to his brothers simcha. i would. (not the Rovs brother, my brother)
but i dont go to every simcha to which im invited. i have my own considerations when i decide whether to go to a particular simcha.
i would hope that when someone invites me to their simcha, they are INVITING me, not demanding my attendance.
i would hope they would respect my right to consider my own considerations and be considerate. i would hope they would rely on my right and ability to make such a decision about what they are ASKING of me
it is an invitation not a summons