While not an old maid, a 12 year old was of marriageable age and no longer a child.

However as marriage at 12 for girls and 14 for boys still required parental permission it was uncommon outside of the nobility.

The nobles OTOH, married for many mostly political reasons; and in many cases as soon as a political alliance could be cemented, it was.

Margaret Beaufort was married at 12 and at 13 was a widow pregnant with the future king Henry VII.

Meanwhile Shakespeare is the weirdo, marrying at 18 when he was too young to do so without his father's permission to a woman quite a bit older than the average early-20s bride in Stratford in his day.

Writing a poem to your fiancee is not the same as writing love poetry to a child too young to marry.

Dante