siblings born less than a year

Cienna
I have a 5 month old and am currently 9 weeks pregnant with twins.
when i thought it was just one baby i wasnt worried because they'd be a year apart, but now that it's twins i know they'll be born earlier or at the exact same time as my son. 
does anybody else have babies less than a year apart? 
also tips for buying stuff for twins would be helpful!