Not common, but not abnormal. I am not sure you would call it a split heat that far apart. Not sure. Young bitches sometimes take a few months to get regular, and if another bitch brings them in, well it can happen.
I know my first bitch had some spotting at four months, then her first heat at eight months, and her second at 12 months. After that she went to a six-month cycle.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC