In a congregation I know it seems there's a whole generation who came in, mainly during the 1970s, who either didn't have children, or their children left JWs.
There's a couple in their 50s who never had children.
There's a couple in their 60s who had two daughters, neither got baptised, they have a few grandchildren now who've only once or twice been inside a KH.
There's a sister who adopted two children, neither was baptised, neither attend.
There's a sister in her 60s, her son was never bapsited, her daughter is an active JW, and she has 5 children all still attending (this is the most successful JW family in the congregation in terms of retention)
Another sister in her 70s has three sons, only one attended as an adult, never baptised, no longer attends, various grandchildren only been to KH occasionally.
Another sister in her 60s, had one daughter, was baptised, now inactive.
Another sister in her 60s, two daughters, one baptised then disfellowshipped, other daughter never baptised, never attends.
Another couple in their 60s never had children.
Another sister in her 60s had one son, never baptised, never attends (never even seen him)
One couple in their 60s had one daughter who is baptised and active.
Another couple in their 40s have no children.
Another couple in their 50s have no children.
Another sister in her 80s had three step children, one got baptised, disfellowshipped and later died. The rest never got baptised.
One brother in his 60s had three children with non-JW wife, none ever came to KH.
One couple in their 60s look after a grandchild who comes to KH occasionally, never baptised.
Another couple in their 60s had a son and daughter, neither got baptised, neither attend.
There's a whole generation of children who simply never became JWs. As the 1970s believers get older, there's literally no one ready to replace them.