All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The sideburn, which is adjacent to the earlobe channel, is part of the beard.
Shaykh Ibn 'Uthaymeen was asked: “What is meant by the beard?”
He replied: “The boundaries (extent) of the beard is from the cheekbones, level with the channel of the ears, until the bottom of the face. It includes the hair that grows on the cheeks.” [End of quote]
The fact that hair existed before the growth of the beard does not affect its ruling, because it generally grows in young man before the growth of their beard, as stated by the scholars.
For more benefit, please refer to Fatwa 339685.
Allah Knows best.