Father is Oto-san. Grand father is Otoo-san
Mother is Oba-san Grand mother is Obaa-san.
It is a subtleness in length and intonation.
And the Japanese tend to call anyone that is an old person Obaa-san.
Just like in america, we might say, hey, granny.
Thus the joke you probably have seen where a middle school person calls a 30 something woman Obaa-san, and she doesn't like being called in old lady.
I keep using a capital O, because there really is an emphasis on it.
It is showing respect. Thus, if you just say to-san you are disrespecting your elders, which is something you just don't do.
Of course, the -san is the same honorific you hear people use on the end of people's names when being polite.
-kun (male) and -chan (female) I am sure you heard lots. They are for use with people you are close and familiar with. (and close in age)