Welcome, can you provide a little more information...were the kids with the dam or started on a bottle from birth?
How long have you had them? What type of nipple are you using? What type of milk or formula are you using? How are the kids acting...up and moving, crying etc? Is the inside of their mouth warm(don't feed if their mouth's aren't warm-they need to be warm) and will they suck on your finger?
tagging other @Goat Whisperer @babsbag @Southern by choice @Wehner Homestead @OneFineAcre