sunflower4

Thanks all for the replies. We were able to call Selective Service when they opened Monday morning and they confirmed that when USCIS registered him, they didn't send his SSN, so that's why we're not able to find his record through the site. The lady on the phone updated his record so it is now accessible through the site, and confirmed that he was indeed registered before his 26th birthday. So we now have the proof of his on-time registration. 

Thanks all for the replies. We were able to call Selective Service when they opened Monday morning and they confirmed that when USCIS registered him, they didn't send his SSN, so that's why we're not able to find his record through the site. The lady on the phone updated his record so it is now accessible through the site, and confirmed that he was indeed registered before his 26th birthday. So we now have the proof of his on-time registration. 

Thanks all for the replies. We were able to call Selective Service when they opened Monday morning and they confirmed that when USCIS registered him, they didn't send his SSN, so that's why we're not able to find his record through the site. The lady on the phone updated his record so it is now accessible through the site, and confirmed that he was indeed registered before his 26th birthday. So we now have the proof of his on-time registration. 

Thanks all for the replies. We were able to call Selective Service when they opened Monday morning and they confirmed that when USCIS registered him, they didn't send his SSN, so that's why we're not able to find his record through the site. The lady on the phone updated his record so it is now accessible through the site, and confirmed that he was indeed registered before his 26th birthday. So we now have the proof of his on-time registration. 

Thanks all for the replies. We were able to call Selective Service when they opened Monday morning and they confirmed that when USCIS registered him, they didn't send his SSN, so that's why we're not able to find his record through the site. The lady on the phone updated his record so it is now accessible through the site, and confirmed that he was indeed registered before his 26th birthday. So we now have the proof of his on-time registration. 

No  separate applications
i have seen posts that say the father can come and petition the son after he becomes a citizen and that is faster 
but the experts will chime in with the best advice
 

Once your SO becomes a citizen he can file for his brother (over 21) but it can take 10 years or more. 

There's no way for them to come together.  Derivative beneficiaries are not allowed when a USC petitions for a parent.
 
The fastest way is NOT to wait for the father to become a US citizen to petition the son.  The fastest way is for the green card father to file for his unmarried son over age 21 in the F2b category.  The current wait is 5 years.  Historically, it's about 7 years. 
 
Separation is unavoidable when it comes to US immigration.  

There is zero benefit to waiting for his father to become a citizen, as that alone will take about the same amount of time it currently takes for a LPR to sponsor an unmarried son over 21, AND then they’d still need a long wait after that. 
I’d suggest filing both F4 when OP’s SO becomes a USC and the F2B when the father becomes a LPR. Just to have an “insurance policy” going in case something goes wrong with the F2B. 

Well you could petition sibling and then wait until a year or so before PD is current and sponsor parent.

Yup, but no IR for a son over 21, that is F1. In fact the USC petition for over 21 unmarried children is currently the only one where the wait is longer than for an LPR petitioning the same type of relative.  If it is shorter by then and brother doesn’t have a visa yet the father will just upgrade the existing F2B to F1, there will be the option of retaining F2B if it is still quicker at that stage.
 
 

That solves the problem of not leaving brother alone, but the entire process would probably take at least double, probably more like triple, the amount of time to get them both here vs the other options discussed. So I guess they need to decide what’s more important.
 
 

It may be easier to apply before marriage, but we applied after marriage and were issued a SS number/card, so it is possible and not a "mistake".
Per what Dave said, you ARE able to get a SSN/card on K-1 visa and you can check the box that says you are able to work in the US for that application. You do not have to wait for an EAD or green card as long as you get the SSN with just the right timing - a few weeks after arrival when you begin to appear in the SAVE database, and more than 2 weeks before your I-94 expires. The DHS verification process also takes about 4 weeks, so you should go immediately after you appear in SAVE.
 
That being said I am in the same boat to where I did go immediately, I waited 4 weeks and the card didn't come so I went back to SSA and they said the DHS verified OK so I should expect the card in 2 weeks, it still didn't come, and now the I-94 is expired and they refuse to send a replacement card. However I asked the SSA clerk to tell me what his number is at least, and she did, so I can use that on my taxes and other forms. Maybe you can try asking for them to tell you the number if you were already assigned one, even if they can't send you a card.

It may be easier to apply before marriage, but we applied after marriage and were issued a SS number/card, so it is possible and not a "mistake".
Per what Dave said, you ARE able to get a SSN/card on K-1 visa and you can check the box that says you are able to work in the US for that application. You do not have to wait for an EAD or green card as long as you get the SSN with just the right timing - a few weeks after arrival when you begin to appear in the SAVE database, and more than 2 weeks before your I-94 expires. The DHS verification process also takes about 4 weeks, so you should go immediately after you appear in SAVE.
 
That being said I am in the same boat to where I did go immediately, I waited 4 weeks and the card didn't come so I went back to SSA and they said the DHS verified OK so I should expect the card in 2 weeks, it still didn't come, and now the I-94 is expired and they refuse to send a replacement card. However I asked the SSA clerk to tell me what his number is at least, and she did, so I can use that on my taxes and other forms. Maybe you can try asking for them to tell you the number if you were already assigned one, even if they can't send you a card.