Mine were 5 months apart and I got them both as six week old puppies. They adore each other. Mine are half sisters, sharing the same father. But, a few words of advice, learned the hard way. 1) Give them each their separate time to train and love. 2) Definitely invest in obedience classes, even if you have to take them one at the time. Best if an adult can take them through. 3)LOVE them to death!
Lilly and Honey are as different as night and day, but they love each other unconditionally and they love us the same way.
Good luck with your decision.
Logan