If you have a doe with two yearlings, how do you know if one is a buck. Do the bucks at that age have small antlers that are visible?

Do you mean a doe and two fawns? If you do, then in the later fall unless you can see nubs, you can't tell.

For yearling deer though, bucks typically have easily visible horns. Whether it be small spikes, or better.

Sorry,

Yes, a doe with two fawns.

Shooting fawns is risky business. My first deer kill was a nubbin fawn. I may have only been 14 at the time, but I've never shot a fawn since then.

My take on killing fawns is, unless you have to earn a buck tag, just let it go. You may be killing tomorrow's buck, and it's almost never worth the risk taking the kill. It's the only time I've felt bad about killing anything in my hunting career.

The bucks will have little nubs or what's usually called "buttons". If you have time to look, you can usually tell the difference through your scope. I typically shoot the biggest doe that comes out in the group. I don't know whY i do that, I know alot of guys like shooting little tender ones. But I've always liked shooting big fat doe.
-Jake