Nowadays children grow up, get their education, get a job and a spouse and leave the nest. Everyone is working in every part of the world. Even the older generation like ourselves, have relatives living all over the world. So it is not possible to know and keep track of every cousin they have.
I do not come from a big family and therefore my children do not have much problem knowing their cousins from my side. The exception is my elder sister's children. They are older and have not met my children and they are now living in Australia and the US. The BIG problem is on my wife's side. She has 7 brothers and 3 sisters with some living in China, Australia and Singapore.
So it is a problem in getting everyone together even if we want to arrange a gathering. My daughter is staying in England and is in contact with 2 cousins whereas my son is in Indonesia. The others are in China, Canada, US, Australia and Singapore. They might meet some time in their lives but as strangers.
Well this is something my wife can only worry about but cannot find a solution as yet.