Let $G$ be a compact connected and simply connected Lie group and $G^\mathbb{C}$ be the complexification of Lie group (with is diffeomorphic with $G^\mathbb{C}\cong T^*G$) then I am looking for finding the 2nd homotopy group $\pi_2(G^\mathbb{C}/P)$ where $P$ here is Parabolic subgroup. Is there any method or referrence ?