She may have only been three-years-old when Beverly Hills, 90210 premiered, but little Blake Lively was still old enough to appreciate the charms of Brandon Walsh. Now she's sharing the proof.Lively's latest #TBT shows 90210 heartthrob Jason Priestley hugging a clearly smitten baby Blake. The actor dated Lively's sister Robyn (a.k.a. Teen Witch ), which gave Blake access to one of the biggest babes of the '90s. So jealous.Lively joked about the photo in her accompanying caption."TBT to when Serena Van Der Woodsen and Brandon Walsh were a thing," she wrote. Oh, if only.