Yes it's normal for an 8 year old child to pee the bed.
A lot of kids and 8 year olds pee the bed and it's usually caused by a slow growing bladder.
The bladder is not large enough to hold in the urine that is produced through the night and the muscles of the bladder are also not usually working properly which is normal and nothing to worry about.
Most kids outgrow bed wetting by age 13 to 17 years old and sometimes sooner.
Some kids may stop wetting the bed as early as age 4 and some may continue wetting the bed until age 17.
If your 8 year old has been wetting the bed for a long time then nothing is usually wrong.
However the doctor can prescribe some medicine to help slow urine production.
You might also want to have the 8 year old wear diapers if they will to help keep their clothes clean and dry.