The origin of these terms was somewhat disparaging, but they appear to have developed into more neutral or even positive terms.
Since I was the middle child of three born within a span of only 26 months, I am an Irish triplet. An my younger brother was born only 10.5 months after me, so I am an Irish twin too. Today starts the period of each year that my younger brother and I are the same age.
All three of us are technology nerds. My older brother Keith did a triple major in Engineering, Physics, and Mathematics, and is a super software engineer. My younger brother Greg is a leading expert on IT change management, and frequently speaks and writes about it. And I got my Ph.D. in Math, taught math, was a software engineer for 12 years, and now work as a patent attorney.
Being an Irish triplet built who I am. Learning to play together, build forts together, and make up silly jokes together is a great way to start life.