Sorry, but I really can't get a footing here...
The Francis showing on both the 1880 and 1900 New Jersey census would
appear to be the same chap as the house numbers are the same on each census return, the son Robert's age tallies and the saloon theme continues. Ages are a bit out though as in 1880 he's 60 and in 1900 only 70. The 'will' mentions
86 Pine Street so perhaps all three are the same person?
From the census - Francis arrives in 1864, Robert (along with Ann?) arrives 1882, Maggie and her children Alexander and May Black arrive 1893. It would also appear that an F, Mrs, Bella, Robert and infant boy Whitecross arrive in the USA in 1882 - steerage - with 'F' showing as a labourer age 45 - 17 years shy of the age showing for Francis on the census.
I'm not sure where the Dundee connection comes from except Francis and Robert Whitecross got on a boat in Dundee in 1893 - both showing as liquor merchants - only three passengers showing on the voyage.
There are newspaper articles about Francis Whitecross (or multiples?) appearing in the Dundee papers from 1856 till 1882.
The two year old Francis in 1871 is living Mills Land, Cherryfield Lane, Liff & Benvie, St Mary's, Forfarshire (Angus), Scotland. His parents are Thomas and Catherine Whitecross. Thomas is a HLW born Kirriemuir.
1871 - living at 17, Newmonthill Street, Forfar, Forfarshire (Angus), Scotland (see address for cockfighting incident
).....Elizabeth MacDonald and a James Fyffe - unmarried ...in 1873 an Elizabeth MacDonald has a wee boy called Robert Fyyfe MacDonald (same name as in the will)...many parts of the puzzle still missing....
Jen