This is possible using TikZ with the mindmaps library. But you have to draw the connections between the first-level nodes manually:
\documentclass[tikz]{standalone}
\usetikzlibrary{mindmap,backgrounds}
\begin{document}
\begin{tikzpicture}[mindmap,concept color=black]
\node[concept,fill=blue!30] (A) at (0,0) {A}
child[grow=200] {node[concept,fill=blue!20] (Aa) {a}}
child[grow=240] {node[concept,fill=blue!20] (Ab) {b}};
\node[concept,fill=red!30] (B) at (5,5) {B}
child[grow=20] {node[concept,fill=red!20] (Ba) {a}}
child[grow=160] {node[concept,fill=red!20] (Bb) {b}};
\node[concept,fill=green!30] (C) at (10,0) {C}
child[grow=340] {node[concept,fill=green!20] (Ca) {a}}
child[grow=300] {node[concept,fill=green!20] (Cb) {b}};
\path
(A) to[circle connection bar] (B)
(B) to[circle connection bar] (C)
(A) to[circle connection bar] (C);
\end{tikzpicture}
\end{document}
