As there is 3 of them. Best thing you can do is lure them away from each other. Best bet is to make sure they split from the alpha. Kill the alpha unless you want it. Lure it into taming raft. 3 walls high. They will glitch through the walls so be careful. Then shoot. It took 60 or so arrows all headshots for a 50 one to go down. They are not easy to do solo. Have a rifle. I killed a 95 alpha with rifle.
Try to make them fall into a ravine. Flyers help with this tactic. Or better, look for some that spawned or fell into one. There’s a ravine on my SP game where there are around 11 allos that fell into it. After getting them into a ravine, kill off all but the one you’d like to tame. Proceed in taming as usual.