US Immigration from Philippines

If a US citizen would petition her full sibling(same mother and father in the birth certificate)... would there be an issue if the birth certificates seems to indicate the mother and father are married but legally they dont have a marriage certificate... the reason they are not married is because the father has a previous marriage that not legally anulled...so in my mind, I think the birth certificate is somehow flawed but I could be wrong..

based on what I read so far it looks like we should not have an issue but curious if they would check if the details of the birth certificate is 100% accurate?.. and if they do find out inaccuracies, is it possible to affect the petition?... and if there is anything we can do proactively about it if any...

I see a lot of people show joint credit cards as proof for the i-751 form. My question is do you just take pictures of both of your credit cards and submit that? I'm not that fond of sending the USCIS my full credit card number. Thanks.

I'm curious if I actually need to submit an AFFIDAVIT?

I have lots of evidence but was just wondering if that is needed for the I-751 or not.

Thanks.

I have been posing a lot for F4 lately.

This time, I wanted to ask for your expertise on the eligibility. I have a super blended family so now, I am in a bit of a pickle.

Background: All my siblings are half-siblings, and all of them were born out of wedlock. I am the only one who's considered legitimate.

My older brother (paternal side): Based on the instruction, I need to submit his mom and my dad's marriage certificate for the documentation.

Issue: They don't have one.

Question: Does this mean he is not eligible for F4?

My younger three siblings (maternal side).

Issue: Their birth certificate shows a date of marriage between my mom and their dad. But as you may already know, in the Philippines, they were able to put that even they were not married. My mom was a widow when she met my step dad. They didn't get married but they parent the three.

Questions:

1. Will the date of marriage in my younger siblings' birth certificate cause an issue in the immigration process since there is no marriage?

2. Do they qualify for F4 as illegitimate?

Issue: In my birth certificate and marriage certificate, my mom's name does not have a middle name. While with my younger siblings' birth certificate, she has a middle name.

Question: Will this be considered discrepancy and will this cause issue with their immigration?

Any help/information is appreciated.

I am so confused when filling out the I-751 form. Who is the petitioner? Is it me the U.S. Citizen Spouse as it was on the AOS and K1 visa forms? Or is it my wife who is the permanent resident who arrived on a K1 visa? Thanks.