Yeah, my money's on the youngest child being the product of one of the daughters and the father. If you look at the "Day Care" enrollment, it lists kids in 5th grade and up...and then there's this 2yo. Now, I have 4 kids over an 11-year span, I understand gaps, but that's a little much! especially since there doesn't seem to be a fertility issue.
I can't fault the neighbors--we live in a neighborhood where we literally have the only children on the block, everyone else is MUCH older--in fact, three neighbors died last year, another moved into assisted living. So, we don't hang out much--we wave hello, exchange pleasantries, but that's it. They've seen my kids, for sure, but I don't know if the neighbors could pick my kids out of a line-up, name them, and say for sure that we only had 4.
The grandparents, OTOH, had to have had a clue. You'd think they'd casually inquire about the kids, and expect typical answers--Betty started college, Joe has a job, Missy is dating a young man from church. SOMETHING. even if you weren't very involved, you'd want to know about milestones.
I do wonder if things took a turn for the worse in the last few years, but this wasn't ever close to normal.