Some sibling tag questions include "what do you like and dislike about your sibling(s)?" "What is your funniest memory?" and "What is your most memorable argument?" Questions can also ask who is the oldest, what siblings do for fun, and what siblings have in common with each other.
Some other questions to ask in a sibling tag are "what is your favorite inside joke?" and "have you ever liked one of your sibling's friends?" Siblings can also describe each other in one word.
More things to ask in a sibling tag are who takes longer to get ready in the morning, name something that is annoying about each sibling, and what is the best thing about each sibling. Siblings can also be asked if they ever argue and what a favorite memory is. A few more questions to ask are if they have nicknames for each other, and what the last text they sent to each other was. A few more ideas for questions to ask are if they are competitive with each other and "what is one thing that you can do that your sibling can't?"
Another fun thing to do in a sibling tag is to post or show an earliest photo of each sibling.