What is the probablity of a child being bipolar (type 2) if one parent is but not the other?

Unclear..: Research on this is extremely varied, ranging from about 3% to nearly 50%. It does seem as though there's a strong likelihood of a mood disorder but it is unclear how much of this is genetic vs environmental. In other words, it's not a given but parents should keep an eye out for developing mood symptoms.

Rarer in children: Than bipolar 1. And for good reason since it is a milder type of bipolar and often dependent on relational problems as a marker. So its subtlety gets really murky in the world of children and emotional symptoms. As far as I know there are no studies on this type of genetic transmission. I could be wrong and welcome other child psychiatrists to add if there is such data. Take care.