My sisters and I never argue or bicker about anything ... we have always been the best of friends and when accidents happen (like me wrecking Jane’s bicycle when it was only two hours old) she understood completely and we had a good laugh ... lots of brothers accidentally ride bikes into a swimming pools but some sisters get an attitude or start with the complaining ... but not my sisters ... no sir! It’s like the time I (accidentally) set fire to Stacey’s Barbie collection when I didn’t get that awesome cowboy hat I wanted for Christmas ... we just laughed it off. Boy, those were good times! I wonder where they are nowadays?
Meanwhile ... back at the Quiz ... the illness you’re thinking of is Sibling Rivalry.