However, according to your incomplete conditions, because Xiao Zhang+Xiao Li =52 and Xiao Li+Xiao Li =54, we can know that Xiao Li is two years older than Xiao Zhang and Xiao Zhang is nine years older, so Xiao Li is older than 1 1 year, so we can preliminarily judge that they are brother and sister (according to the fact that all three are older than sisters 1 1)