Trying to Understand What Happened to Some of My Mcluskie Ancestors

I know that my great Grandparents were William Bennett McLuskie and Isabella (Bella) McLaughlan from Perth but then moved to Glasgow sometime in 1890's. My grandfather James McLuskie born 1888 Perth; from early census there was a sister born around 1890 Isabella but next census 1901 shows the parents William and Bella - son James; son William and daughter Williamina (Ina) born 1898 in Glasgow. Would like to know what happened to Isabella (probably died very young) - also when William was actually born (think 1893) and do not know when he died and if he ever married. Sure could use some help. Regard Debbie