When you wrote this:
J.Thomas wasn't actually our founder,we exixsted in the 1st century as the disciples of Christ..
Were you being serious?
Oh, he was being serious, alright. They do believe that they can trace their lineage back to the first century. But since they count that lineage through figures such as William Tyndale, who was known to history as a Trinitarian, the linkage is tenuous, at best.
No, Thomas was an apostate Congregationalist who decided to start his own religion after nearly drowning in a shipwreck. At first he fell in with a group run by Alexander Campbell, but went out on his own, when he realised his ego wasn't being stroked enough. He was heavily influenced by the Millerites (weren't they all? ) and was guilty of date setting, as were most groups that come from that lineage.
His successor was Robert Roberts, a disobedient child who rebelled against his parents and their religion at age 12, and threw in his lot with the fledgling religion of Thomas. Like most founders of religion at the time, he was not immune from financial skullduggery. He fell for a scam involving buying land in what is now Israel to establish the Millennial Kingdom. Most of his flock's money disappeared down that money pit, along with his own.
Since Christadelphians believe that you cannot be saved under their system unless you understand it, children and the mentally challenged are not likely to be resurrected. This tore Roberts apart when one of his own kids died. He had no hope for that child's resurrection, which is kind of odd for a religion that subtitles itself as "The Hope".