Maybe they're not really twins/siblings. Maybe only Will, Dodger and Liberty were actually Anna's children and Patrick convinced or manipulated everyone of thae Sienna/twin story when he first came to HO (I remember Anna asking Sienna 'I'm sorry, who are you again?') Okay I'm totally making this up (I could work for hollyoaks
) but something has to explain how Patrick knows the identity of the kid's father, without having known that he was also his son, because when he found out who Dodger was, that he was his son, he was genuinely shocked and happy to have found him again. If Patrick had recognised him as the kid who got Sienna pregnant then he'd have been really distressed when he revealed he was actually his son too! The whole Dodger having a mystery twin is dumb anyway, and Sienna having a kid when she was a teenager is lame, and Nico is an abysmal actress haaa, but if they stick to this Dodger being the dad story then they've totally made it up on the spot for the sake of all the twincest fans watching!