Board Thread:Off Topic/@comment-28745050-20160614060931/@comment-4010415-20160626025345

There are a lot of factors we don't know. For example, we don't know if Taiyang had previously dated Summer before dating Raven and conceiving Yang.

What we do know is, Raven broke up with Taiyang in a pretty harsh way. They were together, they conceived a child, and everything likely seemed great while Raven was pregnant. But then, she gave birth to Yang, suddenly went "I'm leaving you", walked out the door without an explanation, and never came back. Ouch. Suddenly, Taiyang is left alone, heartbroken and confused, with an infant he must raise on his own.

So, Summer, his friend and the team's leader, comes in and helps him raise Yang. She could've moved in with him, since taking care of an infant is pretty much a full-time job for a while. I can imagine her also taking care of Taiyang to an extent, due to his depressive state. So, they were working together to be Yang's parents, and Summer may have been caring for and comforting him in his weak emotional state.

One possibility is that a moment of weakness led to Ruby's conception. It seems like there were a few years between Ruby's birth and Summer's death/disappearance, considering Yang was old enough to reason that the photo she found was a possible lead and to pull a wagon out into the woods. During those few years, Taiyang could have fallen in love with Summer if he hadn't already.

If he and Summer had previously dated before he began dating Raven (maybe even before he met Raven), then working together to raise Yang could have rekindled those old feelings.