A series of unpublished and previously unseen poems by Ted Hughes written shortly after the poet’s lover, Assia Wevill, killed herself and their daughter, Shura, in 1969 - six years after the suicide of Hughes’s first wife Sylvia Plath - has been discovered and will be auctioned at Sotheby’s next week, the Guardian has reported. The poetry, handwritten in Hughes’s notebook, is a mixture of short fragments and more complete drafts of poems. There are four poems that seem to be more “finished”, which Gabriel Heaton, Sotheby’s books specialist, believes to be some of the “most direct” work Hughes produced about his emotional state. These poems clearly express his grief for Wevill and Shura, with one poem directly addressed to his daughter. “You were too young to know about death …” reads one line, while another section, addressed to Wevill, asks: “When you were thinking / You wanted to kill yourself why …”

The poems have has come to Sotheby’s from Frieda Hughes, the daughter of Hughes and Plath, along with several other items from the Hughes family collection, which will also go on sale. The other items from the collection include a lock of Plath’s hair, her mirror and childhood stamp collection. Hughes’s copy of the Cambridge student magazine that led to his first meeting with Plath is also featured.

The book of poems is expected to sell for between £10,000 and £15,000. The four pages of verse are written in ink, and some of the handwriting is not legible. Their incomplete structure “suggests that Hughes found the subject too painful and abandoned the works”, according to Sotheby’s.

Until the 1998 publication of Birthday Letters, his response to the suicide of Sylvia Plath, Hughes had not published poems with an overtly autobiographical theme. The notebook, along with approximately 30 other lots from the Hughes family collection, will be offered in Sotheby’s Books, Manuscripts and Music from Medieval to Modern sale, open for bidding from 12-19 July.