We wait and put our goats into kid when they are 18 months old, so they kid around the time they are 2. Kidding at only 1 year is quite early and can mean they are smaller animals and it may also mean they produce less milk (in that first year anyway, maybe not in years after that).
Our kids are born in March normally, put in kid the following year in October and kid in March 2 years after they are born.
It can be quite normal for a goatling (aged 1-2 years) to start producing milk in the summer, so if they start to develop an udder an only 5 months old, they are even more likely to do it at 15-16 months when the grass is at its peak and daylight longest.
Beth