I'm asking a friend's question:
He has an approved I-130 from a sibling sister but has about another 7 years to wait for a visa number.
Recently his mother who is a green card holder got naturalized. This would appear to move him up to 2nd preference category.
But how does one go about changing the petitioner on an I-130? Can the time spent waiting for a sibling application (4th preference) be credited to your waiting time under (2nd preference)?
Or does one just withdraw the I-130 for sibling and wait all over again for (2nd preference) parent?
Because if the same petitioner upgrades from LPR to USC then the I-130 does so automatically. So what happens in this situation?

As I understand it his Mother files, but any time on his Sister's petition is irrelevant, Best to let both run, in case for example his Mother died.

So you suggest filing another I-130 through the mother and wait it out. While the old priority date from the sibling filing becomes irrelevant?
Terrible...yet another long wait with no time credit Bad news to report in that case.

I am not a lawyer, just going from what I have read, if it is a big issue check it out.

They do not lose the 'credit', there is nor credit as such, different applications have different timelines, you can have multiple applications running with different timelines and go with the one that comes through quickest.

Thanks, that is the same conclusion I came to as well on independent research. Always good to confirm though.