There's a nice recording of this song by Loman Cansler under the title "The Stepmother" on a 1973 Smithsonian/Folkways album titled Folksongs of the Midwest (available on Spotify). Here are the notes and lyrics from Cansler's recording:

My wife's maternal grandmother, Edith (Miner) Walker (1869-1941), compiled a remembrance or manuscript book between the ages of twelve and fifteen. She lived in Knox County, Illinois. Among the songs that I copied from the book in December, 1951, was "The Stepmother."

During the summer of 1954, in Peoria County, I collected a shorter version and the tune of this song from eighty-eight-year-old Mrs. Etta (Camp) Conover. The next summer, Mrs. Ivy Stemler, from the same Illinois county, sang a version similar in content and melody to that of Mrs. Conover. She called it "I Could Not Call Her Mother." (Mrs. Stemler was born in Lee County in 1871.)

When I played these versions for my Mother-in-Law, Lillie McElwain, she thought their melodies went about the same as she remembered her mother singing the the song.

Some people tend to lump such songs as "The Stepmother" as sentimental tear-jerkers, or some other title implying make-believe or contrived situations. That such songs do exist, I will admit. But, I have known a number of high school youth who have wrestled with the attitudes and deep-seated feelings that are portrayed in this song. In fact, Mrs. Conover's chuckle that June day in 1954 spanned eighty-odd years and revealed a similar deep-seated emotion, when she told how an older friend, Jennie, who had a stepmother, used to sing this song and substitute "a darn sight blacker face" instead of the words, "a fairer younger face."

THE STEPMOTHER

The marriage vow was over
And I turned myself aside,
To keep the guests from seeing
Those tears I could not hide.
I wreathed myself in smiles
And led my little brother
To greet my father's chosen
But I could not call her Mother.

She was a fair young creature
With meek and gentle air,
With blue eyes soft and lovely,
And dark and sunny hair.
I knew my father gave her
The love he bore another,
But if she were angel
Oh, I could not call her Mother.

Last night I heard her singing
Those songs I used to love,
When every word was uttered
By the one that sings above,
It pained my heart to hear her;
Those tears I could not smother,
When every note was uttered
By the dear voice of my Mother.

They changed my Mother's portrait
From its old accustomed place,
And hung beside my father's
A fairer, younger face.
They made her dear old chamber
The boudoir of another,
But still I can't forget her,
My own, my angel, Mother.

My father in the sunshine
Of happier days to come,
Will not forget the sorrow
Which darkens our dear home.
But he is no more lonely,
But I and little brother
Must still be orphan children,
God gave us but one Mother.



Notes:
Edith (Miner) Walker arranged this song in four lines each. Mrs. Stemler's handwritten copy showed stanzas of four lines, also, but the portion of the song she sang for me was a stanza with eight lines.

For this album I have borrowed four lines found in both the versions from Peoria County to form the last part of stanza four. Making the real mother's chamber "...the boudoir of another..." adds to the completeness of this song and readies the listener for the ultimate expression of ambivalence.