http://books.google.com/books?id=N2Uk58uFSD4C&pg=PA76&lpg=PA76&dq=siblings,+iq+within+10+points&source=web&ots=-t4-DINk49&sig=B0B5rig8k58D2r63KOnUgkBVLmY&hl=en&sa=X&oi=book_result&resnum=1&ct=result

Might be of interest!