Complex sentence: They both grew up together in Sweden and started playing drums at a very young age but with Adrian's career beginning in 1981 at the age of 11 after getting his first drum kit, and started to play with friends began playing covers of classic rock songs.
Split into simpler sentences: They both grew up together in Sweden and started playing drums at a very young age. He began drumming at the age of 11 when he got his first drum kit, and with friends began playing covers of classic rock songs.