fabruncle
A man who gets his sister pregnant. The kid is his brother, his dad, and his uncle. He's a total family disaster.
My dad's sister had a kid with him. That kid is my brother and my dad. My dad is a fabruncle.
My uncle has a kid with my mom. That kid is my brother and my cousin. My uncle is a total fabruncle.
My dad is my brother's dad. But my dad is also my brother. He's a fabruncle.