It appears to be a bug in the USA V4 / V4.5 TamaTown web site. The V4 parent is visible on the V4 / V4.5 European TamaTown web site (but the V4.5 parent doesn't show up as the corret character there.)
This happens quite alot with the V4 and V4.5 parents. It does this because it takes a while for certain characters to load, therefore some characters will not show up when you visit your tama's parents or grandparents.
And there are a few topics on this subject already!