Send a message to dad and to brother asking Would you like to meet for dinner next Saturday?
[IN:SEND_MESSAGE Send a message to [SL:RECIPIENT [IN:GET_CONTACT [SL:TYPE_RELATION dad ] ] ] and to [SL:RECIPIENT [IN:GET_CONTACT [SL:TYPE_RELATION brother ] ] ] asking [SL:CONTENT_EXACT Would you like to meet for dinner next Saturday ] ? ]