how to install 2 linuxes on one sysytem..

how to install 2 linuxes on my system i done the partitions separately for both linuxes i.e., /,/boot,swap for both. but i can’t get first linux grub menu so instead of getting two choices 2 enter it defaultly goes in to latest os grub loader the previou one hided, so my doughth is how to replicate the previous one and how can i use both os’es.. is it possible to do like this any number of linuxes as a list to load our own by selecting at boot option. Is it called grub problems?