There exists a census page from the England & Wales census of 1841 (National Archives, Kew: HO 107/110/10). It shows a Pelan household in Dukinfield (now a town inside Greater Manchester). It is comprised of six persons:
James Pelan , 55, Warehouse man, Ireland
Margaret Pelan, 50, (no occupation given), Ireland
Margaret Pelan, 20, Weaver, Ireland
James Pelan, 20, ditto, Ireland
WIlliam Pelan, 15, ditto, Ireland
John Pelan, 10, Weaver, Ireland
The 1841 census had many shortcomings, such as not asking the relationship between householders and also it asked that people's ages be rounded down to the nearest multiple of 5 - although this was not always done. This is why the ages look suspicious because they are rounded. The lack of relationship information means that connections are usually inferred, i.e. two adults, male & female, are taken to be a couple and any children are assumed to be theirs. These are all assumptions but which will be accurate much of the time.
If you look at open trees on Ancestry, you will find many unrelated people laying claim to this census page as being their family. Why is this ?
Then first thing to remember is that these names are very, very common - not just in the Pelan family but in society in general.
The ages have been rounded down so have a 5-year wide variability, someone that is marked as 50 could be 50 to 54.
People ignore the 'I' indicating they're from Ireland.
There is no surviving census of Ireland for the same period, so when people search for 'William Pelan' and they find one in the English census, they conclude '"that's my one!", when all the other William Pelans cannot be found because that census was destroyed.
In summary, people are being funnelled down onto this search result because it is a rare one for that period and features common names. This may be your family but you'll need more evidence than just a name or two.