These men were among the founders of your church.
SIDNEY RIGDON'S TESTIMONY
Sidney Rigdon, in a lengthy letter to his official paper, The Messenger and Advocate, in 1845 declared that the Prophet was responsible for the plural marriage doctrine, and said:
This system was introduced by the Smiths some time before their death, and was the thing which put them in the power of their enemies, and was the immediate cause of their death. P. 475, vol. 2.
He says he "warned Joseph Smith and his family," and told them that destruction would come upon them if they continued in their course.
ORIGINAL RECORDS OF PLURALITY OF WIVES
You "confidently affirm that there is not a single word in a single sermon, lecture, statement, newspaper or Church publication printed during the life of Joseph Smith, wherein he by word has endorsed the doctrine of plurality of wives, not a single statement." Whether any such statement was ever printed in his lifetime or not I am not prepared to say. But I do know of such evidence being recorded during his lifetime, for I have seen it.
I have copied the following from the Prophet's manuscript record of Oct. 5, 1843, and know it is genuine:
"Gave instructions to try those persons who were preaching, teaching or practicing the doctrine of plurality of wives; for according to the law, I hold the keys of this power in the last days; for there is never but one on earth at a time on whom this power and its keys are conferred; and I have constantly said no man shall have but one wife at a time unless the Lord directs otherwise."
There is also at the Historian's office in this city, a Bible, which I have before me, containing the record of the marriage of Melissa Lott to the Prophet Joseph Smith, which was recorded at the time, September 20, 1843. This Bible also contains the record of the sealing of Cornelius P. and Parmelia Lott, parents of Melissa, which was done by Patriarch Hyrum Smith in the Prophet's presence and with his "seal" or sanction. The president of your church has seen this record, and it matters not what he may say now he then acknowledged the genuineness of the record.