Java nested ifs

Below is a small function which when given two numbers (a, b), returns true if one of the numbers is a teen-number. Returns false if both are teen. Returns false if both are not teen. I failed these test cases but I can't figure out why. Help? (13, 99), (14, 20), and (16, 9)

public boolean loneTeen(int a, int b) 
{
    if(a<=19 && a>=13) 
    {
        if(b<=19 && b>=13)
        {
            return false;
        } 
    }
    else if(a<=19 && a>=13)
    {
        return true;
    }
    else if(b<=19 && b>=13)
    {
        return true;
    }
    return false;
}