Look at these sentences:

I am hungry. He is hungry. We are hungry.

We have to choose 'am', 'is' or 'are' depending on who we are talking about. It would be wrong to say 'I is hungry' or 'he are hungry'.

These are the correct forms:

I am

you are

he / she / it is

we are

they are

If we use people's names then we use 'is' for one person and 'are' for more than one.

Elise is my sister.

Billy is my brother.

Timmy and Hattie are my cats.