First credit card (International Lounge Access)

Without much hassle should be from the bank* in which your brother's salary gets credited.

niyo debit card gives international lounge access

HDFC generally gives cards to people with no credit history. It was the first bank that issued me a credit card, back when I had not enough credit history.

He should try for a diners club card (from HDFC) that offers international lounge access. Diners Millennia or Diners privilege . 

EDIT: Not sure if millennia offers international lounge access. You might need at least diners privilege.

Does he have a long layover at the airports?

Check his credit score; if he ever used any credit product, it will hold some value.

15-day is a short period to get credit card approval and deliver it physically. The fastest way should be via your salary account or FD-backed.

Domestic - AU lit, ICICI Coral (FD), RuPay?

International - NiYO global, Millenia, Yes First(FD), Any FD-backed card

A lot of these cards offer International lounge access via a Priority Pass.. 

You get the card which gives you domestic lounge access.. you apply for a Priorty pass (free with these cards) and it gets sent over which gives you international lounge access..

Some cards like Infina give both cards together.. some cards offer international lounge access via the card itself.. but those are usually the super premium ones..

the regular  cards will need Priority pass.. You can get the credit card in 2 weeks.. but PP in that time looks difficult. 

IDFC Wealth card

Intl & Domestic Airport Lounge & Spas - 4 visits/Qtr
and it's LTF too...!
You will get dreamfolks card for intl. lounge access
I got my card approved and delivered within a span of 10 days. I applied via C2C route though, so, can't comment on other type of applicants

You can also apply for an addon card in his name with some relative or friend who owns diners club black, privilege or airmiles cards or infinia. They offer lounge access for add on cards as well.

Applying for an add-on card would be the fastest (if your family has an eligible primary card). Try for IDFC wealth by visiting the branch. 15 days is too less....

Hdfc tataneu infinity card (rupay variant) gives international lounge access. The other variant gives too but you need to apply priority pass separately. For rupay variant, no priority pass needed

Visit IKEA store and apply for Citibank CC and get instantly approved if your Brother has good Credit score/Earning Good Salary from a reputed Company

Try ease my trip co branded standard chartered card. ₹350+gst fee. It comes with priority pass for international lounge access.