On All My children today there was a song played while Ryan and Greenlee made out. Part of the lyric was You and my one and only. Does anyone know the name or who sang it?

I am not sure as to All of My Children is concerned but the lyrics you provided are from a song entitled, "My One and Only You" performed by Parokya Ni Edgar.

Here are the Lyrics:

It took one look
And forever laid out in front of me
One smile and I died
Only to be revived by you

There I was
Thought I had everything figured out
Goes to show just how much I know

'bout the way life plays out...

I take one step away
But I find myself coming back to you
My one and only, one and only you... ooh...

Now I know
That I know not a thing at all
Except the fact that I am yours
And that you are mine

Ooh

They told me that this wouldn't be easy
And no
I'm not one to complain...

I take one step away
Then I find myself coming back to you
My one and only, one and only you

I take one step away
But I find myself coming back to you
My one and only, one and only you…