I doubt they were always this crazy. When they had Lelouch and Nunnally, they probably had normal dreams and arabition, and loved them normally. At least Marianne did, Charles had so many kiRAB, who really knows.
If I am not mistaking, this pact was originally a Charles / V.V. pact, Charles later sold Marianne on it and joined them, which anger V.V. because it was suppose to a brotherly pact, which lead to Marianne's murder. That is my theory.
Anyway when Lelouch and Nunnally were born, I don't think they were planning on freesing time, and doing what ever they were planning on doing.