Few scenarios, could be that they are the oldest and the rest of their siblings aren’t ready to have a family.
Well, that cousin is from my wife’s side. She does have dozens of first cousins from my side, but we live far away from them, so she has only met some of them once or twice for short periods of time. Nothing long enough to form a connection. Plus, she is older than all of them by about 5 years, so there is that too.
I could be 1 in the same age range.
my dad was the youngest of 7. and he had kids late. so almost all my cousins on my dads side are at least a decade older than me, and we barely had any contact with them growing up. on the other hand, cousins on my mothers side are all my age, and i have the best relationship with at least one of them despite only seeing each other every few years.
Shit experience with large family would do it. My grandparents had 12 living children, less than half my aunts and uncles decided to have kids, and those who did had 1-3.