I think what will probably end up happening is you will not be able to go get a loan by yourself and you will have to get someone to co sign on the mortgage (parent, older sibling, friend, someone  who has good credit and work history).

Parter with someone to bring the money or be a co signer on the mortgageThis could be a parent, sibling, friend who is more finically stable and the banks will feel comfortable giving a loan to.

They may help him.Also, maybe ask if he has other siblings or relatives as they may be able to help him transition.

End result is 4 adult siblings in a 4 bedroom SFR.

Ask any of us who have experience in estate deals, nothing turns loving siblings/family into a murderous rage like family deals not well defined. 

I also assume you have no siblings and your father is no longer in the picture. 

None of my siblings have the means to purchase the house for market value, that way the other siblings can be compensated equally and one sibling doesn't inherit an unequal share of equity.  

I will give my two cents on this subject, my siblings are split on the subject. 

FHA loans and their siblings have been just a little too far outta reach for my high DTI, and I get that.

Yes, I believe owning your home is great, for a number of reasons.  1st) Rent should pass your payment amount in pretty easily.   2nd)  A home shows many lenders more stability.  3rd)  I have refinanced my home, where the payment is still comfortable but I am using my equity to buy other properties.  4th)  For many of us it gives peace of mind, ( 3 of my 4 siblings have there homes paid off completely).