An inevitable issue that arises with kids' birthday parties is the question of whether family is invited. Should parents come along, or drop the kids off? Furthermore, are siblings ever invited by default? First and foremost, parents should assume that siblings aren't implicitly invited, especially older ones. And no matter what, parents should clarify with the host family that a sibling will attend.
If siblings over the age of three tag along, they should be aware that they may not be able to participate in all of the activities. Host parents will likely try to accommodate siblings, but some things may not be age-appropriate. For instance, older brothers and sisters probably shouldn't join in competitive games since they'll have an unfair advantage. At the same time, younger children may hold up the activities if they aren't on an equal skill level. Consequently, parents should tote along some discreet alternative options (coloring books, handheld video games, etc.) to keep any siblings entertained.