Yes, the Prophet Joseph Smith was sealed to more than one wife. No, this does not shake my faith. I believe I have known it since I was a teenager, in spite of the fact that many critics of the church are shocked, shocked I tell you, to learn that Joseph actually engaged in the very practice that was revealed to him as recorded in the Doctrine & Covenants. Apparently, in the minds of some, polygamy sprang fully formed, like Athena from Zeus, from the wild mind of Brother Brigham.
Shocked they also are that the Church doesn't rent billboards trumpeting this knowledge to the world. After all, a knowledge of the names of the wives of the Prophet will be required of every member hoping to achieve celestial glory. (I'm being a little sarcastic there.)
Yeah. Boggles the mind.
I know all about the Helen Kimball thing, too, the 14 year old to whom the Prophet was sealed in some capacity. It is quite a stretch, a very slanderous stretch, to call a man a pedophile -- our critics' new favorite word for the Prophet -- for being sealed and that not to a child but to a teenager. In many states of the US, it is still perfectly legal to marry a teenager. Furthermore, there is no clear evidence anywhere that the Prophet ever had any intimate relations with Helen Kimball. Sealing is a doctrine, like many doctrines, that took time to be fully and properly understood and fully unveiled.
The bigger picture: Aside from one line in the New Testament about certain qualifications of being a bishop, the Lord issues not one word of condemnation in the entire Bible about plural marriage and, in fact, even called the polygynous Abraham His friend.
Latter-day Saints do not practice this principle today, because the Lord can command and the Lord can revoke and He has currently revoked. Thus He had no problem with judicious use of wine in Biblical days but has told us to refrain in this modern era -- so please do not trot out that tired line about Timothy and his stomach or Jesus drinking wine so why don't we? Thus He forbade pork in Biblical days but does not forbid it now.