The Chaperone Bride — Marina Oliver

When Joanna finds herself destitute after her gambler father's suicide, unable to find work, and is offered instead a marriage of convenience, she sees no other option. Sir Kenelm needs a wife as a chaperone, since governesses are reluctant to live in a widower's household. The twins, children of his first wife, refuse to accept her as a new mama. The governess, having thought she too was applying for the position of governess, resents her.