The certificates I looked at on Scotlands People, the census I looked at on Ancestry.
1891 Census - 102 Bain Street, Glasgow Barony, Lanarkshire
Philip G. Ferguson    Head      bc.1858 England
Ann Ferguson          Wife        bc.1863 England
Francis G. Ferguson      Son        bc.1885 Glasgow
George H. Ferguson     Son         bc.1886 Glasgow
Philip G.T. Ferguson      Son         bc.1889 Glasgow. 
As to Jane Ferguson, who can say.
This is the best I can do - Good Luck.
Annette