I'm betting it's

THE BLIND CHILD'S PRAYER

"They tell me, father, that tonight
You wed another bride;
That you will clasp her to the arms,
Where my dear mother died.

''They say her name is Mary too,
The name my mother bore.
But, father, is she kind and true
Like the one you loved before?

"Her picture is hanging on the wall;
Her books are lving near;
There is the harp her fingers touched;
There sits her vacant chair,

''The chair by which I've oft times knelt
To say my evening prayer.
O father, do not bid me come;
I cannot meet her there.

''Now let me kneel down by your side
And to our Saviour pray
That God's right hand will lead you both
Through life's long weary way."

The prayer was answered and the song,
"I'm weary now," she said,
He picked her up all in his arms
And laid her on the bed.

And as he turned to leave the room
One joyful cry was given,
He turned and caught the last sweet smile
The blind child was in heaven.

They buried her by her mother's side
And raised a marble fair;
And on it graved the simple words,
"There'll be no blind ones there."

From Folk Songs from the Southern Highlands, Henry
Collected from Mrs. Emory P.Morrow, AL

Just in case it's not, could it be Charlie Poole's

I CANNOT CALL HER MOTHER (which, however, lacks the blindness)

The marriage rite is over
Although I turn aside
To keep the guests from seeing
The tears I could not hide

I wreathe my face is smiling
And I left my little brother
To greet my father's chosen
But he could not call her mother

She is a fair young creature
With meek and gentle airs
With blue eyes soft and loving
And silk and sunny hair

I know my father gives her
A love he had for another
If she were an angel
I could not call her mother

My father's in the sunshine
Of happy days to come
They have forgot the shadows
That darkened our old home

His heart is no more lonely
But me and little brother
Must still be orphan children
God gives us but one mother