“Hal’s father, having been exiled from Mother Base, returned to America and eventually reunited with Hal. By the time Hal was a teenager, his father had married British native Julie Danziger. Danziger had a daughter of her own, named Emma, who adopted the Emmerich surname. Hal and Emma oftentimes played “House” together in their childhood.
When Hal was a teenager, he was seduced by his stepmother Julie and they had an affair. In 1997, Hal’s father, after learning about this, committed suicide by drowning himself in the family pool. He dragged Emma with him, but she managed to survive. Emma expected Hal to come to the rescue, but Hal didn’t know it was happening as he was with Julie at the time. Surviving the incident, Emma always claimed to hate her brother because she believed he had abandoned her."
– Metal Gear Wiki

Metal Gear is kinda fucked up.

This reminds me of when Huey got cucked by his own son and drowned himself in the backyard pool.