Wiz Khalifa reunited with his ex-wife Amber Rose to celebrate their son Sebastian's 7th birthday over the weekend.Rose, who is expecting a child with Def Jam A&R vp Alexander "AE" Edwards, shared several photos on social media from the birthday celebration, including a shot of Sebastian's creepy Pennywise-themed cake."Happy early Birthday to my Smart, Articulate, Sensitive, Compassionate Baby Boy Sebastian!" Rose captioned the Instagram post on Sunday (Feb.