Fostering two feral kittens- 9 weeks old

Hi, I am fostering two feral male kittens. I've had them for 10 days and one kitten has really come around! The other male seems to be getting less tolerant of humans even though he's become more confident in his surroundings. Despite every effort I keep hitting brick walls with him. I want him to become as adoptable as his brother has become but sadly it's not happening. The older he gets the less desired he will be. Not to mention they are bonded and I would love to see them go to a home together ... But he needs to sell himself!!
Suggestions??!

Some cats do not care to cuddle. If they are bonded, I would explain they are a pair and for the new adopters not to expect both of them to be cuddle bugs. It may be the only chance he gets to be adopted. Hopefully his brother is cuddly enough for both of them.

Of course, keep working with him. He may surprise you and make a turn around. We have an eight year old former feral who we brought in at six months. We did everything wrong! He's now brave enough to approach us for pets and has even started sleeping on the bed when we aren't in it. After years of hiding under the bed, we are thrilled. (He's the cat in my avatar).