Ashley Young has only one year left of his current deal and is understood to be attracting interest from Manchester United, but Downing is also coming under the microscope after an impressive campaign.
Luke Young said: "Stewart has been brilliant. I played with him at Middlesbrough so I knew the potential that he's got. I feel he would have done a bit more if he had got out a couple of years earlier.
"Now he is showing the form and you've got bigger clubs sniffing at him and it is obviously going to be difficult for us to keep him. We haven't had a great season so I think some of the bigger clubs are having a look at him, and rightly so with the form he has shown.
"He is one that we hope stays because he is a big player for us. The bigger clubs are circling for Ashley as well so it is going to be a difficult summer for us and hopefully we can keep hold of both of them, but we certainly wouldn't want to lose both of them.''
Luke Young believes Downing has the ability to emulate Ashley Young and move to the forefront of Fabio Capello's England plans.
He said: "I think Stewart is starting to believe that he can become an England regular himself. With Stewart, when he is on song and confident, that is when you see the best of him.
"It is just about getting minutes on the pitch for England. It is difficult. There are lots of very good players and you go with a lot of squads and come on for 10-15 minutes.
"You actually need to be given a run of games like Ashley Young has been given and he has taken his chance and maybe Stewart needs that as well."
Luke Young is happy to be playing on a regular basis for Villa after not getting many opportunities last season.
He said: "I've always just wanted to play football. I've never been unhappy at the club. I just wanted to have a fairer crack and be involved a bit more.
"I had three or four months towards the end of last season where, no matter what I did, I didn't really get a chance. That was my only frustration. I love the club. It's a great club, a big club."