Hi Karen, I have to concur with the Repton Moorhouses being associated to Joseph and Frances [nee Neville] marrying at Ashby-de-la-Zouch. The couple baptised 8 children at Repton between 1812 and 1830, the Thomas you mention being the oldest son.
There is clearly no evidence that the Joseph and Frances [Neville] Moorhouse ever lived at Ashby-de-la-Zouch and it seems highly probable the marriage took place there simply because the parents of Frances were residents of that parish at the time. There is a good chance of locating Joseph's home parish in that marriage record at Ashby. The format of marriage records changed in 1813 and this just sneaks into the old system where the Cleric often recorded visitor's parishes.
The 1841 Census of Repton does not show the couple living in the town, so it is reasonable to suggest they moved [emigrated] between 1830 and 1841 to a new location. This would also explain why none of the children married at Repton or can be found in subsequent censuses there. With this informaton we can reasonably assume your Thomas in OHIO is very likely the son of Joseph and Frances.
The issue of whether William is related is debatable, but it is not unreasonable to assume they may have known each other in both countries, and being of the same surname, of course took an interest in a possible relationship. Perhaps one encouraged the other to emigrate. William disappears from Repton after 1824. In the Repton Register there is a single entry which may be relevant: Frederick Morton Moorhouse baptised 31st Dec 1824 to William and Elizabeth [Nee Williams] Moorhouse. This couple married at Repton on 13th Feb 1823. It is worthy of noting that no further children were baptised here. Did this family actually emigrate WITH Joseph and Frances? The time period fits, and if so no doubt they remained friends if nothing else, travelling to Ohio together??? Currently I have not attempted to trace the Joseph who married Frances Neville. There are literally hundreds of likely candidates in Yorkshire and a lengthy process of elimination seems to only sensible recourse. I have attempted this for other Josephs and found it very hard going, but over the years have managed to sort out a few of them.Good luck with your research. I will keep in touch if any material relevant comes to hand and would be interested to hear if you make a break through. Under the circumstances it does not seem impossible that William is a younger brother of Joseph. The other couple contemporary at Repton were Charles and Elizabeth [nee Collyer] Moorhouse who did remain at Repton and can be found in later census material. Is this a third brother?Perhaps! Cheers from Mark