Several studies had already shown that children with an older sibling have poorer language performance than those without an older sibling. But a research team from the CNRS, Robert-Debré AP-HP hospital, EHESS, ENS and Inserm has just specified this result: it would only concern children with an older brother. This work was published on August 14 in the journal Psychological Science.

See the CNRS press release

Bibliography:
The effect of siblings on language development as a function of age difference and sex. Naomi Havron, Franck Ramus, Barbara Heude, Anne Forhan, Alejandrina Cristia et Hugo Peyre. Psychological Science, August 14, 2019.