Earliest baby can talk???

Adina • I`m 24 with a 2 year old boy and another on the way. Married for 3 yrs.
What's the earliest age you guys think a baby can begin to say full sentences? I know there's the baby talk and when they should be hitting new milestones but what about actual small convo? If your baby was one of those advanced babies, how did you get him or her to talk so early??