Look at the year this poem was written, does the time period have any significance on why the young girl had two siblings die?William Wordsworths...

The poem "We are Seven" by William Wordworth was published
in 1798, which makes it a transitional poem from the late 18th century to the early 19th
century.

As it is common knowledge, high birth rates were
proportional to high mortality rates among infants in the early 19th century and late
18th century, and even before that. There are many reasons for
this.

First, most births took place at the family home and
very little care was placed on sanitary living conditions mainly because in poorer homes
there was probably overcrowding with too many family members living together, no running
water, or living in filthy slums where cesspools would overflow and diseases would
spread.

Second, disease was rampant as a result of poor
hygienic conditions. There was everything from tuberculosis, typhoid (a particularly
nasty bout occurred at around this time), and the medical profession had not yet been
fully recognized the way that it is today.

For instance,
surgeons were still the local butchers, anyone could call themselves a nurse, and it
wasn't until much later when Florence Nightingale's efforts to instill high hygienic
conditions in hospitals was acknowledged, and the mortality rate did not come to an
all-time low but until the end of the 19th century.