After their mothers died, adolescent chimps adopted their younger siblings and became upset if they lost sight of them even temporarily
Source:
https://www.newscientist.com/article/2207312-death-of-mother-prompts-adolescent-chimps-to-look-after-their-siblings/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home