RDNA new study of 851 twin pairs in the UK, and their younger siblings, found different developmental trajectories between the twins and their singleton siblings from ages 2-7. Twins' language, cognition, and social-emotional skill development progressed more slowly, though language skills caught up by age 7.
Summary: https://www.sciencealert.com/twins-developmental-delays-single-born-siblings
Original paper: https://academic.oup.com/chidev/advance-article/doi/10.1093/chidev/aacaf029/8539540?login=false
